## 1. Life and Work




Anaxagoras, son of Hegesibulus (or Eubulus), was a native of
Clazomenae, on the west coast of what is now Turkey. According to
Diogenes Laertius (see the article on *Doxography of Ancient
Philosophy*) (Diels-Kranz [DK] 59 A1), Anaxagoras came from an
aristocratic and landed family, but abandoned his inheritance to study
philosophy. (We do not know how he acquired his philosophical
learning). He came to Athens (perhaps about the middle of the
5th century, perhaps earlier), and was a friend and
protege of Pericles, the Athenian general and political
leader. There is controversy about his time in Athens; Diogenes
Laertius says that he came to Athens to study philosophy as a young
man. Some scholars claim that his arrival was as early as the Persian
invasion of 480 (O'Brien 1968, Woodbury 1981, Graham 2006), others
argue for a later date of about 456 (Mansfeld 1979, see also Mansfeld
2011 on Aristotle's evidence; there is a good discussion of the
problems about dating Anaxagoras' life in Sider 2005). It is clear
from their dramas that his work was known to Sophocles, Euripides, and
perhaps Aeschylus (Seneca suggests in his *Natural Questions*
4a.2.17 that they shared Anaxagoras' view about the source of the
Nile); it was certainly familiar to the comic playwright Aristophanes
(Curd 2007, Sider 2005; see Mansfeld 1979). He was a resident in the
city for at least twenty years; he was said to have been charged with
impiety (and perhaps with Medism, political sympathy with the
Persians), and banished from the city (437/6?). The charges against
Anaxagoras may have been as much political as religious, because of
his close association with Pericles. He retreated to Lampsacus (in the
eastern Hellespont) where he died; ancient reports say that he was
much honored there before and after his death. Democritus, a younger
contemporary, dated his own life in relation to Anaxagoras', saying
that he was young in the old age of Anaxagoras (DK59A5); he reportedly
accused Anaxagoras of plagiarism. Although Anaxagoras lived in Athens
when Socrates was a youth and young adult, there are no reports that
Anaxagoras and Socrates ever met. In Plato's *Phaedo*, Socrates
says that he heard someone reading from Anaxagoras' book (probably
Archelaus, who was, according to Diogenes Laertius, pupil of
Anaxagoras and teacher of Socrates). Anaxagoras is included in the
ancient lists of those who wrote only one book: in
the *Apology*, Socrates reports that it could be bought for a
drachma.




As with all the Presocratics, Anaxagoras' work survives only in
fragments quoted by later philosophers and commentators; we also have
testimonia about his views in many ancient sources. The standard
collection of Presocratic texts (both fragments and testimonia) is
H. Diels and W. Kranz, *Die Fragmente der Vorsokratiker*, in
which Anaxagoras is given the identifying number 59. The Greek text
and translations can also be found in Gemelli-Marciano, 2007-2010; Graham, 2010; and Laks and Most, 2016a and 2016b. (For discussion
of the sources for the Presocratics, and problems associated with
them, see the article on *Presocratic Philosophy*.) Any
discussion of Anaxagoras' views must be a reconstruction that goes
beyond the few details that we have in the verbatim quotations, though
informed by the evidence of the fragments and testimonia. It should be
kept in mind in reading the following account that scholars disagree and that other
interpretations are possible.




According to Simplicius, a 6th century C.E. neo-Platonist
commentator on Aristotle, and our main source for the fragments,
Anaxagoras began his book by describing an original state of complete
(but not entirely uniform) mixture of all the ingredients of the
cosmos; that mixture is then set in motion by the action of
Mind/Intellect (*nous*). The ingredients are eternal and always remain in a
mixture of all with all, yet the rotary motion produces shifts in the
proportions of the ingredients in a given region. The expanding
rotation of the original mixture ultimately produces the continuing development
of the world as we now perceive it. The foundations of his theory,
descriptions of this development, and a discussion of *nous*
form the bulk of what remains to us of Anaxagoras' book. The
testimonia suggest that the book also included detailed accounts of
astronomical, meteorological, and geological phenomena as well as more
detailed discussions of perception and knowledge, now missing from our
collection of fragments, and known only by later reports and criticisms.


## 2. Metaphysical Principles




Anaxagoras was influenced by two strains in early Greek
thought. First, there is the tradition of inquiry into nature founded
by the Milesians, and carried on by Xenophanes (Mourelatos 2008b) and
by Heraclitus (Graham 2008). The early Milesian
scientist-philosophers (Thales, Anaximander, Anaximenes) sought to
explain the cosmos and all its phenomena, by appealing to regularities
within the cosmic system itself, without reference to extra-natural
causes or to the personified gods associated with aspects of nature by
traditional Greek religion (Graham 2006, Gregory 2007 and 2013). They
based their explanations on the observed regular behavior of the
materials that make up the cosmos (see White 2008 on the role of
observation and measurement in early Presocratic theories).




Second, there is the influence of Eleatic arguments, due to
Parmenides, concerning the metaphysical requirements for a basic
explanatory entity within this Milesian framework, and the
metaphysically proper way to go about inquiry (Curd, 2004, 2007; Sisko
2003; for different views, see Palmer 2009, Sisko 2013). Parmenides
can be seen as arguing that any acceptable cosmological account must
be rational, i.e., in conformity with the canons for proper inquiry,
and must begin with metaphysically acceptable entities that are wholly
and completely what they are; are not subject to generation,
destruction, or alteration; and are wholly knowable i.e., graspable by
thought and understanding (Parmenides B2, B3, B7, B8; see Mourelatos
2008a). Anaxagoras bases his account of the natural world on three
principles of metaphysics, all of which can be seen as grounded in
these Eleatic requirements: No Becoming or Passing-Away, Everything is
in Everything, and No Smallest or Largest.


### 2.1 No Becoming or Passing-Away




A fundamental tenet of Eleatic theory is that what-is-not cannot be
(Parmenides DK 28 B2). Parmenides, using this claim (see DK 28
B8.15-16), argued that coming-to-be and passing-away are therefore
ruled out, because genuine coming-to-be is change from what-is-not to
what-is, while destruction is change from what-is to what-is-not.
Thus, says Parmenides, what-is "is without start or stop, since
coming to be and passing away have wandered very far away, and true
trust drove them out"
 (DK 28 B8.27-28).[1] 
 Anaxagoras accepts this principle, explaining apparent generation and
destruction by replacing them with mixture and separation (or
dissociation) of ingredients:



> 
> 
> The Greeks do not think correctly about coming-to-be and
> passing-away; for no thing comes to be or passes away, but is mixed
> together and dissociated from the things that are. And thus they
> would be correct to call coming-to-be being mixed together and passing-away
> being dissociated. (DK 59 B17)




What seems to us, through perception, to be generation of new entities or
destruction of old ones is not that at all. Rather, objects that
appear to us to be born, to grow, and to die, are merely arrangements
and re-arrangements of more metaphysically basic ingredients. The
mechanism for the apparent coming-to-be is mixing and separating out
from the mixture produced by the vortex motion of the ingredients. Through that mechanism, the real things, the ingredients,
can retain their character throughout. When an arrangement breaks
apart (or "passes away") the ingredients are dissociated
from one another (through separation) and can be re-mixed to form (or
"become") different arrangements, i.e., other perceptible
objects.




One way to think of Anaxagoras' point in B17 is that animals,
plants, human beings, the heavenly bodies, and so on, are *natural
constructs*. They are *constructs* because they depend
for their existence and character on the ingredients of which they are
constructed (and the pattern or structure that they acquire in the
process). Yet they are *natural* because their
construction occurs as one of the processes of nature. Unlike
human-made artifacts (which are similarly constructs of
ingredients), they are not teleologically determined to fulfill some
purpose. This gives Anaxagoras a two-level metaphysics. Things
such as earth, water, fire, hot, bitter, dark, bone, flesh, stone, or
wood are metaphysically basic and genuinely real (in the required
Eleatic sense): they are things-that-are. The objects constituted
by these ingredients are not genuinely real, they are temporary
mixtures with no autonomous metaphysical status: they are not
things-that-are. (The natures of the ingredients, and the
question of what is included as an ingredient, are addressed below; see
3.2 "Ingredients and Seeds"). This view, that the
ingredients are more real than the objects that they make up, is common
in Presocratic philosophy, especially in the theories of those thinkers
who were influenced by Parmenides' arguments against the
possibility of what-is-not and so against genuine coming-to-be and
passing-away. It can be found in Empedocles, and in the
pre-Platonic atomists, as well as, perhaps, in Plato's middle
period Theory of Forms (Denyer, 1983, Frede 1985, W.-R. Mann 2000, Silverman
2002).


### 2.2 Everything-in-Everything



> 
> 
> 
> "All things were together." B1 (in part)
> 
> 
> 
> 
> "In everything there is a share of everything." B11 (in
> part)
> 
> 
> 




As we have seen, Anaxagoras' commitment to Eleatic principles rules
out the possibility of genuine coming-to-be or passing-away. It also
rules out real qualitative changes and transformations. When a warm
liquid cools (it seems) the hot liquid becomes cold; when a child
ingests food (milk and bread, for instance), the milk and bread are
(it seems) transformed into flesh, blood, and bone. Yet Anaxagoras
objects to these claims because they entail that the hot ceases to be,
and the cold comes to be, in the liquid, and that the bread and milk
are destroyed while flesh, blood, and bone come to be. His solution is
to claim not only that "all things were together" in the
original mixture, but that everything is in everything at all
times. If there is already blood and bone in the milk and bread, then
the growth of the child can be attributed to the accumulation of these
ingredients from the bread and milk, and their assimilation into the
substance of the child's body, rather than to the transformation of
bread and milk into something else. Further, if there are both hot and
cold in the liquid, there is no disappearance into nothing of the hot
as the liquid cools, and no generation of the cold from what is not
(or even from what is not cold). The clearest statement of this is in
Anaxagoras B10, a quotation found in the following passage:



> 
> 
> When Anaxagoras discovered the old belief that nothing comes from
> that which is not in any way whatsoever, he did away with coming-to-be,
> and introduced dissociation in place of coming-to-be. For he
> foolishly said that all things are mixed with each other, but that as
> they grow they are dissociated. For in the same seminal fluid
> there are hair, nails, veins and arteries, sinew, and bone, and it
> happens that they are imperceptible because of the smallness of the
> parts, but when they grow, they gradually are separated off.
> "For how," he says, "can hair come from what is not
> hair, and flesh from what is not flesh?" He maintained
> this, not only about bodies, but also about colors. For he said
> that black is in white and white in black. And he laid down the
> same thing with respect to weights, believing that light is mixed with
> heavy and *vice versa*. (DK 59 B10; the passage is from the
> anonymous scholiast on a 4th c. C.E. work of Gregory
> of
>  Nazianzus.[2])




Although interpreters both ancient (including this scholiast and
Simplicius) and modern (Guthrie 1965 is a good example) have seen
the desire to explain nutrition and growth as the primary
motivation for adopting the Everything-in-Everything principle, it is more
likely that Anaxagoras' adoption of the general metaphysical
principle of No-Becoming leads him to claim that everything is in
everything (Schofield 1981, Curd 2007). Nutrition and growth are simply particularly clear instances of the changes
that are ruled out as fundamentally real if there is no becoming.




The Everything-in-Everything principle asserts the omnipresence of
ingredients. In everything there is a mixture of all the ingredients
that there are: every ingredient is everywhere at all times. This
principle is a fundamental tenet of Anaxagoras' theory, and leads to
difficulties of interpretation (see, for instance, the debate between
Mathews 2002 and 2005 and Sisko 2005). If everything is in everything,
there must be interpenetration of ingredients, for it must be possible
for there to be many ingredients in the same space. Indeed, the
principle requires that all ingredients be in every space at all times
(the No Smallest or Largest principle also plays a role here: see
sect. 2.3). This will allow any ingredient to emerge from a mixture
through accumulation (or, having been unmixed, to become submerged in
one) at any point at any time, and thus allow for the appearance of
coming-to-be (or passing-away) of things or qualities.




Some scholars have supposed that Anaxagoras thought of these
ingredients as very small particles (Vlastos 1950, Guthrie 1965, Sider
2005, Lewis 2000). But a *particle* would have to be a smallest
amount of some type of ingredient, occupying some space all by
itself--with no other type of ingredient in it. Not only
does the No Smallest or Largest principle rule this out (see sect.
2.3), but the particulate interpretation seems inconsistent with the
Everything-in-Everything principle. It is crucial to
Anaxagoras' theory that there be (in actuality) no such pure bits
or volumes of any type of ingredient.




Instead one might conceive of the ingredients as fluid, like pastes or
liquids which can be smeared together, with different areas of the
mixture characterized by different relative densities of the
ingredients, all of which are nevertheless everywhere in it. Each
genuinely real ingredient could be mixed with every other, and so
would be contained in any area of the mixture, and in principle
visibly recoverable from it by accumulation or increased
concentration. The differing densities of the ingredients would allow
for differences in the phenomenal character of the mixture. To an
observer, different areas would appear hotter or colder, sweeter or
more bitter, more red than green, and so on, and rightly so. As the
relative concentration of ingredients in any area of the mixture
altered (through the mixture and separation brought about by the
rotation of the original blend of ingredients), the phenomenal
character of that region of the mixture would alter. An
intriguing account (Marmodoro 2015, 2017) suggests that Anaxagorean
ingredients are not material; rather they are primitive physical
qualitative powers or dispositions (in the parlance of contemporary
metaphysics, they are "gunky"). 


### 2.3 No Smallest or Largest




B1's claim that "all things were together" before the
original rotation occurred does not guarantee the truth of the
Everything-in-Everything principle. If separation occurs within an
original mixture of everything with everything, as a result of the
motion imparted by *nous*, then it could be that, given enough
time, ingredients would be segregated from one another (as they are in
Empedocles during the triumph of Strife, when the four roots are
completely separated). Anaxagoras needs to block this, so that he can
maintain his commitment to the No Becoming principle. In some region
that came by separation to contain, say, nothing but bone, there would
come to be pure bone (as a new entity), in replacement for and
destruction of the mixture that was previously there. He blocks this
possibility by claiming that there is no smallest (and no largest). If
there is no lower limit on the density of an ingredient, then no
ingredient will be completely removed from any region of the mixture
through the force of the rotary motion caused by
*nous*. Here are Anaxagoras' claims:



> 
> 
> 
> Nor of the small is there a smallest, but always a smaller (for
> what-is cannot not be) -- but also of the large there is always a
> larger. And [the large] is equal to the small in extent
> (*plethos*), but in relation to itself each thing is both
> large and small.
>  (B3[3])
> 
> 
> 
> 
> Since the shares of the large and the small are equal in number, in
> this way too, all things will be in everything; nor is it possible that
> [anything] be separate, but all things have a share of
> everything. Since it is not possible that there is a least, it
> would not be possible that [anything] be separated, nor come to be by
> itself, but just as in the beginning, now too all things are together.
> (B6 [in part])
> 
> 
> 




The passage from B6 makes clear that the "no smallest"
principle is connected to the principle of Everything-in-Everything,
and B3 asserts that the "no smallest" claim depends on the
impossibility of what-is-not. Here is one way to interpret what
Anaxagoras is saying: if there were a smallest (particle, density,
amount) of any ingredient (call it *S*), we could in principle
through separation reduce the amount of *S* in some area of the
mixture to that smallest, and then induce further separation through
rotation, which would remove that ingredient from a particular area of
the mixture. That would leave some area without "everything
in everything." The area would cease to be *S* to
any degree and so would be not-*S*. In that area, the
explanation of coming-to-be in terms of emergence from a previous
mixture would fail. Note that Anaxagoras -- like other Greek
thinkers, including Plato -- assumes that anything that is
must be something or other and so slides easily between "what is
not *f*" and "what is not" (Furley
2002).




Anaxagoras' solution is to deny that there is any lower limit
on smallness. Adopting the model of density described above, he
can say that there is no lowest degree of density in the mixture.
This emphasis on density makes it clear that Anaxagoras'
technical sense of smallness is not one of particle size but of degree
of submergence or emergence in the mixture. For an ingredient to
be small is for there to be a comparatively low density of that
ingredient in a particular area of the mixture in comparison with all
the other ingredients (everything else) in that area. The
corresponding assertion that there is no upper limit on largeness can
then be interpreted as the claim that no matter how emergent from the
mixture (standing out from the background mixture) an ingredient is, it
can become still more emergent. So, no matter how sweet some water
tastes, there is still some salt in it. The salt in the sample is
small, i.e., submerged in the mixture of water and other ingredients,
but there will never cease to be salt in the sample.
Correspondingly, no matter how salty another sample is, it can always
become more salty and even "turn to salt" because there is
no upper limit to the degree of emergence from the background. As
the salt emerges, other ingredients will submerge, but will never
disappear, so that the wet itself is deeply submerged in the mix, and
we are left with an apparently solid block of salt (though that salt
will itself contain all other ingredients, with most of them in such
small concentrations that they are completely submerged and not
apparent to an observer). This account of large and small is
implied in Schofield 1980, and worked out more fully in Inwood 1986 and
Furth 1991; it is accepted in Curd 2007; see also Marmodoro 2017.


## 3. The Physical Principles




The Eleatic metaphysics that Anaxagoras accepts shapes the science
that he proposes. Anaxagoras offers an ambitious scientific theory that
attempts to explain the workings of the cosmos, even while accepting
the Eleatic ban on coming-to-be and passing-away. His goal is
scientific knowledge, i.e., understanding, as far as that is possible for human
beings.


### 3.1 Mixture and Rotation




The original state of the cosmos was an unlimited (*apeiron*)
mixture of all the ingredients. The mixture of ingredients, all
with all, exists eternally. Up to some point in the past, it was
motionless (59 B1, A45), and it was everywhere undifferentiated, or
almost so. According to B1, which Simplicius, the source for the
fragment, says was near the beginning of Anaxagoras' book:



> 
> 
> All things were together, unlimited both in amount and in
> smallness, for the small, too, was unlimited. And because all
> things were together, nothing was evident on account of smallness; for
> air and aether covered all things, both being unlimited, for these are
> the greatest among all things both in amount and in largeness.




This undifferentiated mass includes all there is of all the natural
ingredients that there are, the ingredients that will eventually form
the natural constructs that constitute the cosmos as we know it.
Nothing is ever added to or subtracted from this storehouse of stuffs,
although the mass of stuffs is not always homogeneous. In fact,
there are different densities of ingredients even at this earliest
(pre-motion) stage. B1 makes clear that air (dark, moist stuff)
and aether (bright fiery stuff) are the most emergent (largest)
ingredients, and their dominance means that the original mixture must
have been like a dense bright cloud: nothing else would be evident or
manifest, even had there been an observer. At some point
*nous* (the time being right) set the mixture in motion and
caused it to begin to revolve (first in a small area, and then in an
ever-widening area). The rotary motion causes the ingredients in
the mass to shift. This shifting produces what Anaxagoras calls
"separating off." Because the mass is a plenum, any
separation will be a rearrangement (thus a mixing) of
ingredients. The continouous ever-expanding rotation produces more and
more separation. The Everything-in-Everything principle continues
to hold, so there are all ingredients at all places at all times, but
the different densities of ingredients allow for local variations, and
so the rotating mass becomes qualitatively differentiated.


### 3.2 Ingredients and Seeds




Nowhere in the extant fragments does Anaxagoras give a complete list
of the ingredients in the mixture, or a clear indication of their
scope, so it is up to commentators to figure out what he meant, given
the available evidence. There are three alternatives. First, some
scholars have held that Anaxagoras limited the basic ingredients to
the opposites, such as hot and cold, wet and dry, sweet and bitter,
dark and light, and so on. It is the opposites that have explanatory
force in the theory, and all other things and properties are reducible
to the opposites. Supporters of this view include Tannery 1886, Burnet
1930, Cornford 1930, Vlastos 1950, Schofield 1980 (with reservations),
Inwood 1986, Spanu 1987-88, Sedley 2007, and Marmodoro 2015, 2017. On
this view all the material stuffs and all the objects in the universe
would be natural constructs. At the opposite extreme, a second option
accepts that literally everything in the natural world is in the
original mixture -- opposites, but also natural materials (fire,
earth, copper, iron, and the like), animals and plants (and their
parts such as flesh, blood, and bone), and so on. This view makes no
distinction between ingredients and what have been called natural
constructs above. It can be found in Strang 1963, Stokes 1965, Guthrie
1965, Barnes 1982, Furth 1991, Graham 1994 and 2004, Lewis
2000. Finally, there is a middle view, which rejects the
opposites-only account, and accepts that some things (plants and
animals, heavenly bodies) are natural constructs. The original mix
includes opposites, but also natural substances like metals and earth,
and the ingredients of animals, such as flesh, blood, and bone, but no
whole physical objects such as plants and animals themselves, or their
organic parts such as legs and hearts (Curd 2007; this view is
suggested in Schofield 1980, 132 ff.).




The "opposites only" view cannot stand (arguments
against it are given in Guthrie 1965 and Graham 2004). B15 may provide
some evidence for the view:



> 
> 
> The dense and the wet and the cold and the dark came together
> here, where <the> earth is now; but the rare and the hot and the
> dry <and the bright> moved out to
> the far reaches of the aether.




But Anaxagoras' own lists include more than the opposites (see B4a and
B4b). Further, the Principle of Predominance (in B12, see sect. 3.4)
would seem to require more than opposites, since it does not seem to
say that each thing is reducible to opposite characteristics that
predominate, but that each thing gets its character from the
particular material ingredients that predominate in it. Further
evidence against the opposites-only view is found in Aristotle.
Aristotle claims that for Anaxagoras, the elements (the basic
realities) are what Aristotle calls the homoiomerous parts (*On
Coming to Be and Passing Away* I.1 314a18). These are (for
Aristotle) things that are literally "like-parted," i.e.,
they are homogeneous all the way through, like a piece of pure gold,
rather than being different in their different parts (like a hand),
and Aristotle lists flesh, blood, bone, and adds "and the others
of which the part is called by the same name [as the whole]."
The term *homoiomeries* is Aristotelian, and has no role to
play in Anaxagoras (Graham 1994, Curd 2007; *contra*: Sisko
2009), but it is clear that for Aristotle, the ingredients in an
Anaxagorean mixture are not just the opposites.




If the attempt to reduce the Anaxagorean ingredients to opposites is
unsuccessful, so, too, is the interpretation that allows as an
ingredient every kind of thing in the phenomenal world. A minor
point is that Anaxagoras surely does not think that artifacts made by
human beings are part of the mixture, and there are other semi-natural
artifacts as well that would not seem to be present: cheese, bronze,
whiskey, for example. More importantly, the wide-scope view fails
to take seriously B17's replacement of coming-to-be and
passing-away with mixture and dissolution. Further, it is unclear
how the view can discriminate between an individual and its parts or
ingredients. Are there homunculi of individuals in the original
mix? (Lewis 2000 accepts this.) If so, how can the theory
explain that the growth of an organism is not simply its enlargement
(by adding ingredients) but also its development? (A
plant's leaves may grow larger, but its seed pods develop, and
are not just an enlargement of a structure that was already present in
the seedling plant.) In B4a Anaxagoras refers to the animals and
humans "that have been *compounded*, as many as have soul,"
and this suggests that B17's implicit model of living things as
natural constructs mixed together from the ingredients that are
genuinely real must be taken seriously.




It seems, then, best to interpret Anaxagoras as claiming that all
the material ingredients of natural living things and the heavenly
bodies are present in the original mix, but that these objects
themselves are not among the ingredients but are natural constructions,
produced by the processes of mixture and separation that we call
nutrition and growth, or by the rotations of the heavens and the
attendant clumping together and breaking apart of the ingredients of
the stars, clouds, comets, planets, and so on.




A problem for any account of the original mixture is Anaxagoras'
mention of seeds. The word for seeds (*spermata*) occurs twice
in the fragments, in lists of ingredients (in B4a and in B4b), but
Anaxagoras nowhere explains or makes it clear what it means. There are
a number of options: seeds have been taken to be the smallest possible
bits of ingredients (but, as argued above, there are no smallest bits
in Anaxagoras' system), or to be extremely small homunculi-like
ingredients that some interpretations take to be origins for
Anaxagoras of living things which then expand by the addition of other
ingredients (Lewis 2000). Furley 1976 and 2002 advocates the simplest
interpretation, that Anaxagoras simply means biological seeds (but not
homunculi), and this seems the best proposal (see also Barnes 1982,
Curd 2007, Sedley 2007, Marmodoro 2015, 2017, 147-153; Marmodoro also sees seeds as biological, containing pre-existing structures). A seed would then be a biological origin
point, and might perhaps be the route through which *nous*
(which controls all things that have soul, i.e., anything alive)
enters a living thing. If a seed is mixed with the right ingredients
in the right circumstances, a living thing will grow.


### 3.3 Mind/Intellect




According to Diogenes Laertius, Anaxagoras acquired the nickname Mr.
Mind (DK 59 A1); his view that the cosmos is controlled by
*nous*, mind or intelligence, first attracted and then
disappointed Socrates (Plato, *Phaedo* 97b8ff.). Plato and
Aristotle applauded Anaxagoras for using *nous* as the
first principle of motion, but both criticized him for failing to be
consistent in that use, arguing that once he invoked Mind to set the
original mixture in motion, Anaxagoras reduced later causes to
mindless mechanism.




Anaxagoras is adamant that *nous* is completely different
from the ingredients that constituted the original mixture. It is the
only thing to which the Everything-in-Everything principle does not
apply. Mind is present to some things, but it is not an ingredient or share as
flesh and blood are ingredients in a dog (B11: "In everything
there is a share of everything except *nous*, but there
are some things in which *nous*, too, is
present"). In B12 (the longest extant fragment), Anaxagoras
claims that if *nous* were just another ingredient it
could neither know nor rule in the way that it does.



> 
> 
> The other things have a share of everything, but *nous*
> is unlimited and self-ruling and has been mixed with no thing, but is
> alone itself by itself. For if it were not by itself, but had been
> mixed with anything else, then it would partake of all things, if it
> had been mixed with anything (for there is a share of everything in
> everything just as I have said before); and the things mixed together
> with it would thwart it, so that it would control none of the things
> in the way that it in fact does, being alone by itself. For it is the
> finest of all things and the purest, and indeed it maintains all
> discernment about everything and has the greatest strength. (59 B12,
> in part)




Mind/Intellect plays a number of roles in Anaxagoras' system. First, it
inaugurates the rotation of the mass of ingredients; it then controls
that rotation, and the local rotations that take place within the
large whirl that is the whole cosmos:



> 
> *Nous* controlled the whole revolution, so that it
> started to revolve in the beginning. First it began to revolve from a
> small region, but it is revolving yet more, and it will revolve still
> more... And whatever sorts of things were going to be, and
> whatever sorts were and now are not, and as many as are now and
> whatever sorts will be, all these *nous* set in
> order. And *nous* also ordered this revolution, in which
> the things being separated off now revolve, the stars and the sun and
> the moon and the air and the aether. This revolution caused them to
> separate off. (59 B12, in part)



*Nous* then is not only first cause, it also, one might
say, is the preserver of order in the cosmos, as it maintains the
rotations that govern all the natural processes. Anaxagoras does not
explain how these processes work, or how *nous* can
affect the ingredients. But there is a hint of his reasoning in a
comment in Aristotle (*Metaphysics* I.3.984b15):



> 
> 
> When someone said that *nous* is present -- in
> nature just as it is in animals -- as the cause of the cosmos and
> of all its order, he appeared as a sober man among the random
> chatterers who preceded him. (We know that Anaxagoras clearly held
> these views, but Hermotimus of Clazomenae gets the credit for holding
> them earlier.)




Just as we control our bodies by our thoughts, so the cosmos is
controlled by *nous*; we may be unclear about the
details, but the results are obvious to us. One fundamental point
about Anaxagoras' theory of mind is that he nowhere in the extant
material identifies mind with a divine principle or god. In fragment
1018 and in *Trojan Women* (886), Euripides says that mind is
god in each of us, and connects the necessity of the universe with
Zeus and mind, and these claims are thought to have been influenced by
Anaxagoras' views. Although later testimonial reports in Aetius
and Iamblichus say that Anaxagoras connected *nous* and
god, there are many more reports of his denial of divinity to the
heavenly bodies and his alleged atheism.



*Nous* is the most powerful thing in the cosmos,
controlling the rotation and all ensouled things. Part of that power
and control lies in its powers of knowledge. Anaxagoras asserts that
*nous* has all judgment and discernment about all things;
moreover, this knowledge extends to everything that emerges from the
mixtures and dissociations caused by the original rotation:



> 
> 
> And *nous* discerned them all: the things that are being mixed
> together, the things that are being separated off, and the things that
> are being dissociated. And whatever sorts of things were going to be,
> and whatever sorts were and now are not, and as many as are now and
> whatever sorts will be, all these *nous* set in
> order. (B12, in part)




This suggests a beginning of an answer to the objections lodged
against Anaxagoras' use of *nous* as a cause. While
*nous* is not the teleological and ethical cause for which Socrates was
searching in the *Phaedo*, *nous* could serve as an
ultimate explanation. Anaxagoras nowhere says that
*nous* arranges things in a certain way because it is best for
them to be so, or even suggests something like an Aristotelian final
cause, (although Sedley 2007 argues that exactly this view is implicit
in the fragments, *contra*: Graham, 2009, Sisko 2010a). Things are the way
they are because that is the way things have unfolded
since *nous* first set everything in motion, and as it
continued to move them. (One might compare this to the role of the
unmoved mover as the ultimate cause in Aristotle's universe; despite
being the first cause the unmoved mover does not create.)




Anaxagoras links mind and soul in B12: "*nous* has
control over all things that have soul, both the larger and the
smaller." This suggests not only that Anaxagoras took the
actions of humans and animals as the model for how *nous*
controls the cosmos, but also suggests how *nous* differs from
the other ingredients. He claims that it is the purest and finest of
all things. Some scholars argue that it is only in Plato that we meet
a genuine notion of the immaterial (Renehan 1980, Sedley 2007), but
Anaxagoras' denial that *nous* is mixed with or partakes of
other ingredients (while still being in some of them) and his
insistence on its fineness and purity may suggest that he is thinking
of mind as a non-corporeal entity that can pervade and control a body
or even the whole cosmos without being a material part of it (Curd
2009). On either interpretation, if
*nous* were simply an ordinary ingredient on a par with the
other basic ingredients, then, as Anaxagoras notes in B12, its relative
smallness would allow it to be swamped and overcome
("thwarted") by the other ingredients.


### 3.4 The Principle of Predominance




Fragment B12 ends with a further discussion of mixture and separation,
and Anaxagoras' enunciation of what has come to be called the
"Principle of Predominance." After reasserting that no
ingredient is ever fully dissociated or separated from any other
(except for *nous*, which is not an ingredient),
Anaxagoras adds that all *nous* is alike (that is, cosmic
*nous* and mind in us share the same nature), but
"Nothing else is like anything else, but each one is and was
most manifestly those things of which there are the most in it."
Thus, something is hot, if hot predominates over the cold in it, flesh
if flesh predominates over other ingredients, and so on. The principle
does not claim that there is any single predominating ingredient at
each place in the mixture. Rather, the predominance seems to be along
numerous lines of possibility: more flesh than blood, more hot than
cold, more red than green, and so on (Furley 2002). This need not
mean that there is more humanity than doghood in a human being (indeed
it could not mean this, on the account advanced in this article, which
rules out dogs and humans as Anaxagorean ingredients). Rather, to be a
human being is to have a certain set of predominant characteristics
arranged in a certain way (that arrangement may be the work of soul
-- perhaps *nous* -- in a living thing).




A problem for the Principle of Predominance is to determine what it is
to be a predominant ingredient, especially given the
Everything-in-Everything and No Smallest principles. A classic example
is the following: the gold in this gold ring is that discontinuous
part of the total mixture in which gold predominates. But now, as
Strang says, "Consider the gold which predominates as an
ingredient: does it also, like the original piece of gold, contain
within it an admixture of all other substances? If so, it is gold
because gold predominates in it as an ingredient; and we can ask the
same question about the ingredient of the ingredient, and so on *ad
infinitum*" (Strang 1963, 101; see also Cornford
1930). Because there can be no pure gold (there is no pure anything),
it becomes difficult to see what the gold could be that predominates
in anything. But if I cannot determine what predominates in it, I
cannot determine what anything is.




Strang 1963 proposes a solution to the problem. While acknowledging
that there can never be pure instances of any ingredient in actuality,
there could be such instances in analysis. I can analyze mixtures and
determine predominant ingredients, but I will never be able to produce
a pure instance of such an ingredient. The problem here is how this
would be worked out, and why I can be certain that there are such
natures (as we might call them). Anaxagoras suggests two
things. First, in B12 he stresses that *nous* has the
power to know and understand all the ingredients (indeed cosmic
*nous* apparently knew all this before the rotation began; see
quotation above). Second, in B21 and B21a he suggests how
human *nous* (*nous* in us) can come to such an
understanding by relying on sense perception but moving beyond it in
thought (see sect. 5. Knowledge). Finally, because the ingredients are
genuinely basic entities in the sense required to ground a rational
cosmology in the Eleatic sense, they must be stable natures in the
Parmenidean sense (for a related account, see Marmodoro
2015). Anaxagoras is committed to the arguments that ground Eleatic
metaphysics; thus he can claim an *a priori* reason to think
that the ingredients can be knowable in the sense required by the
Principle of Predominance. His epistemological view that humans can
reach understanding through beginning with sense experience then fits
with these metaphysical commitments.


## 4. Science: The Anaxagorean Cosmos




Anaxagoras gave a complete account of the universe: of the heavens,
the earth, and geological and meteorological phenomena. The accounts
of the action of *nous* and the original rotation and its
consequences appear in the fragments: B9 describes the force and
velocity of the rotation, B12 and 13 explain the beginning of the
rotation and the subsequent breaking up and remixing of the mass of
ingredients, while B15 and 16 specify the cosmological consequences of
the continued rotation (Curd 2007 and 2008, Graham 2006, Gregory
2007). Most of the other information comes from the testimonia, but
there is enough in the remaining fragments to make it clear that
everything is ultimately explained by the great rotation set in motion
by *nous*. Further, and intriguingly, Anaxagoras claims that
the cosmic rotary motion could produce other worlds like our own.


### 4.1 Cosmology




The rotation of the mixture begins in a small area, and then spreads
out through the mass (B12). As the extent of the mixture is unlimited
(or infinite, *apeiron*), the rotation and expansion will
continue forever, bringing more and more ingredients into the whirl (a
summary of the process is in Gregory 2007). The force and speed of the
rotation is (according to B9) much faster at the edges, where the
expanding rotation meets the as-yet-unmoved mass of ingredients: what
we perceive of the rotation (probably the motions of the heavens) is
much slower than the unobserved rotation. The force is enough to pull
apart and rearrange the ingredients:



> 
> 
> When *nous* began to move [things], there was separation
> off from the multitude that was being moved, and whatever
> *nous* moved, all this was dissociated; and as things
> were being moved and dissociated, the revolution made them dissociate
> much more. (B13)




There are two sorts of dissociation. First, as the rotation enters the
as-yet-unmoved mass of ingredients, that mass begins to break up and
the ingredients start to shift in their concentrations. This causes
the original arrangement of ingredients to break up and begin to be
rearranged. Because the mixture is a plenum, any separation is at the
same time a rearrangement of ingredients. Then, those new
rearrangements are themselves subject to further break-up and further
rearrangement. Anaxagoras indicates this in the fragments by using
different terms for different stages in the process (although he is
not completely consistent in these uses). Normally, he uses the notion
of being separated off (forms of the verb *apokrinesthai*) for the
initial breaking apart of the mass. Re-arrangements are referred to as
mixing (*summisgesthai*) or compacting
(*sumpegnusthai*). He also uses "joining
together" (*proskrinesthai*) as a contrast to the
separating off process (*apokrinesthai*) in B4a and B4b. When,
in B17, he claims that passing-away is really dissociation, he uses
the word *diakrinesthai*. This is a later stage than the
earliest separations off of B1. The primary terms are compound forms
of the verb *krinein*, to distinguish. The word can also mean
"to judge" or "to determine," and through the
use of these compound terms, Anaxagoras reminds his readers that all
of the changes are ultimately traceable to the action of
*nous*, or Mind, that sets the mass moving in the first
instance.




Over time, the rotation throws lighter ingredients towards the edges
of the whirl and pushes the heavier ones to the center (B15), thus
putting more dark and heavy ingredients like earth in the center and
throwing air and aether (fire) away from the center. This gives the
traditional Greek picture of our Earth (itself a mixture of all
ingredients, with earth and heavy ores and minerals predominating)
covered (in many places) by water, with air and the fiery reaches of
the heavens.




The sun is a mass of fiery metal, and the moon is an earthy lump
(with no light of its own). The same rotation ultimately produces
the stars and planets as well. Sometimes the force of the
rotation snatches up stones from the surface of the Earth and spins
them around the Earth as they gradually rise higher through the force
of the rotation. Until these bodies are high enough, they remain
unseen between the Earth and the moon and so sometimes intervene to
prevent heavenly bodies from being seen by terrestrial observers.
The force and shaking of the rotation can cause slippage, and so
sometimes a star (a flaming mass of rock and iron) is thrown downwards
toward the earth as a meteor (such as the one Anaxagoras is supposed to
have predicted at Aegospotami; see Galzerano 2019). The fullest account of
Anaxagoras' view on meteors can be found in Plutarch's
*Life of Lysander* 12 (59 A12). Anaxagoras is also credited
with discovering the causes of eclipses -- the interposition of
another body between earth and the sun or the moon: sometimes he
credits this to the "unseen bodies" mentioned above (see
Graham and Hintz, 2007, Graham 2013a and 2013b, Taub 2003). According
to the ancient sources (see esp. A1 and A42), Anaxagoras also gave
explanations for the light of the Milky Way, the formation of comets,
the inclination of the heavens, the solstices, and the composition of
the moon and stars.


### 4.2 Meteorology and Geology




The rotation begun by *nous* ultimately affects phenomena
on the earth and above the surface of the earth. Anaxagoras claims
that the earth is flat, rests on air, and remains where it is because
of its size (A42; a number of geological and meteorological views
attributed to Anaxagoras were also apparently held by Anaximenes;
whether this is because Anaxagoras was following Anaximenes or because
the commentators conflate the two is unclear). Despite the manner of
its formation, the earth is stationary, not spinning. The (relative)
flatness of the earth allows water to spread over the earth, with
mountains and plains rising above the level of the water. The levels
change as water is evaporated or added by rain, and as water that has
been trapped in the earth by the rotation makes its way out through
rivers to the sea. Because the air under the earth is also moving
(pushed along by the cosmic rotation), it sometimes gets caught up in
the crevices of the earthy stuff. When this air cannot make its way
out, the force of the moving air causes earthquakes. Anaxagoras seems
determined to explain everything. The extant sources report views on
thunder and lightning, the source of the Nile, the first correct
account of the nature of hail, and inquiry into why the sea is
salty. He also offered accounts of sense perception and made
inquiries into embryology.


### 4.3 Other Worlds?




One of the more curious aspects of Anaxagoras' theory is hinted
at in B4a:



> 
> 
> Since these things are so, it is right to think that there are many
> different things present in everything that is being combined, and
> seeds of all things, having all sorts of forms, colors, and flavors,
> and that humans and also the other animals were compounded, as many as
> have soul. Also that there are cities that have been constructed
> by humans and works made, just as with us, and that there are a sun and
> a moon and other heavenly bodies for them, just as with us, and the
> earth grows many different things for them, the most valuable of which
> they gather together into their household and use. I have said
> this about the separation off, because there would be separation off
> not only for us but also elsewhere.




Where is the "elsewhere" where there would also be
separation off, and where there are sun and moon "for them, just
as with us"? Surprisingly, no ancient sources discuss this
(although Simplicius, who quotes the fragment, is clearly puzzled by
it, and argues for a neo-Platonic metaphysical interpretation). Modern
commentators have suggested that the other worlds are on the moon
and/or other planets (Johrens 1939, Zeller 1923), elsewhere on
the face of our Earth (Cornford, 1934), or even contained within
ourselves (and all other things) so that there are infinite worlds
within worlds (Mansfeld 1980, Schofield 1996, Sisko 2003). There is
also the possibility that Anaxagoras has no commitment to the reality
of these other worlds, but is simply engaging in a thought experiment
to show how the rotation would work (Frankel 1969, Vlastos 1975,
Schofield 1996). There may be another possibility (Curd 2007). The
unlimited rotation begins in a small area and expands indefinitely,
pulling more and more of the unlimited mass of as-yet-unmixed
ingredients into the whirl. Such an action could produce smaller local
rotations within the larger whirl (especially at the expanding edges,
as in the rotations of hurricane winds) and there, too, separation,
mixture, and dissociation would occur. Such processes would result in
the formation of systems like our own. This is not a
thought-experiment on Anaxagoras' part, but a commitment to the
law-likeness of the rotations controlled by
*nous*, and an awareness that similar processes will
produce similar phenomena. Our world-system is not unique in the
universe, although there is but one universe (constituted by the
entire limitless mass of ingredients).


## 5. Knowledge




Both ancient and modern critics have complained that Anaxagoras is
unclear about the nature of *nous* (Mind/Intelligence) and its
role in his theory (Laks 1993, 2002; Lesher 1995). In B12 Anaxagoras
claims that
*nous* has all discernment, and that *nous* "knew
them all: the things that are being mixed together, the things that
are being separated off, and the things that are being
dissociated." Further, Anaxagoras remarks that there is
*nous* in many things, and that it is alike in all the
things that it is in, both large and small (presumably those with
soul, i.e., living things). Aristotle says that Anaxagoras conflates
soul and mind, and B12 seems to confirm this, insofar as Anaxagoras
there treats *nous* primarily as a mover, yet also says
that it controls all things that have soul. It seems likely that in
things other than cosmic *nous*, those compacted or
mixed-together natural constructs that have soul, the powers of
*nous* include both knowing and perceiving. Nowhere do we have
an analysis of the process of thinking for Anaxagoras, and although
Aristotle and Theophrastus say that earlier thinkers identified
thinking and sense perception, there is little evidence for this view
in Anaxagoras (Laks 1999, Warren 2007).




It seems clear that if *nous* is to have all discernment and
to order the cosmos, it must have some knowledge of the contents of the
original mixture (Lesher 1995, Curd 2004). Further, if the
ingredients are fundamentally real things they must have stable and
knowable natures. (This follows from Parmenides' arguments
about the connection between what-is and what is knowable.) Thus,
there is a match between the natures of the ingredients and the
cognitive power of cosmic *nous*, but Anaxagoras leaves the
mechanism unexplained. It seems likely that cosmic *nous*
just has a direct intellectual grasp of these nature and acts in
accordance with that knowledge.


### 5.1 Mind in Us




Only a few fragments and testimonia discuss Anaxagoras'
views on perception and knowledge in living things. Aristotle and
Theophrastus give us some account of his theory of perception, saying,
most surprisingly, that for Anaxagoras all sensation is accompanied by
discomfort or pain (A92). Theophrastus links this to
Anaxagoras' belief that like is perceived by unlike; on
Theophrastus' view, perception is via touch, and unlike things
produce some irritation when touched. Theophrastus adduces loud noises
and very bright light as producers of pain in perceivers, and suggests
that the mechanism is the same in all cases of sensation. Some
irritation will be below the level of awareness for most perceivers,
which is why humans do not normally feel pain when
perceiving (see Warren 2007 for a good discussion of Anaxagoras on perception).




What is the relation between perception and knowledge?
Anaxagoras does not claim that perception alone is sufficient for
knowing; nor does he seem to embrace skepticism. Sextus
Empiricus, always on the lookout for arguments for and against any
dogmatic position, gives us most of the evidence for Anaxagoras'
views. Says Sextus, of the skeptic's methodology, "We
set what is thought in opposition to what appears, as Anaxagoras set
the appearance that snow is white in opposition to the claim that snow
is frozen water, water is black, and therefore snow is black"
(A97; but see the passage from Cicero in the same testimonium).
Here Anaxagoras accepts that snow seems to us to be white, but claims
that the reality must be that snow is black. The evidence of the
senses must be corrected by what we know through thought. In B21,
Anaxagoras recognizes the weakness of the senses ("Owing to
feebleness [of the senses], we are not able to determine the
truth"), but in B21a he accepts that sense perception can be a
step towards understanding: "appearances are a sight of the
unseen." This follows from his own theory, for the evidence
of our own control of our bodies by our minds, the facts of nutrition
and growth, and the local revolutions of the heavens are evidence for
the workings of cosmic *nous*, the No-Becoming principle, and
the great cosmic revolution. Like other Presocratics, Anaxagoras
leaves us with no detailed account of how knowledge derives from
perception through the refinements of thought: Anaxagoras'
account can be compared with that of Democritus, where the relation of
sense-perception and thought is similar and similarly unexplained.


## 6. Anaxagoras' Influence




Reportedly the first of the Presocratic philosophers to settle
in Athens, Anaxagoras was a significant figure, not only for later
philosophical thinkers, but also for the wider civic culture of his
time. He was clearly an important influence on Pericles.
Plutarch reports:



> 
> 
> But Anaxagoras of Clazomenae was the one who most associated with
> Pericles and who most bestowed on him that dignity and wisdom more
> weighty than demagoguery, and on the whole raised up and exalted the
> worthiness of his character ...These are not the only advantages
> that Pericles enjoyed because of his connection with Anaxagoras. It
> seems that Pericles rose above superstition, that attitude of
> astonishment about celestial occurrences which is produced in those
> who are ignorant about the causes of things and who are crazed by
> divinity and divine interventions because of their inexperience in
> these areas. Natural philosophy substitutes for festering superstition
> that unshaken piety that is attended by good hopes. (A15,
> A16)




That naturalism appears in the dramas of Euripides, who is often
described as a pupil of Anaxagoras, and in the comedies of
Aristophanes, who satirizes the views of Anaxagoras as well as the
figure of Socrates in *Clouds*. Anaxagoras' theory
of the floods of the Nile was known to Herodotus (and may be referred
to in Aeschylus). Despite stories that they did not get along,
there are signs of influence of Anaxagoras on Democritus (in his
accounts of perception and knowledge) and Anaxagoras' scientific
claims and discoveries affected all the thinkers of his time.
Once his views about meteors, hail, and eclipses became known, such
topics were always included in scientific accounts of astronomical and
meteorological phenomena. In the testimonia, Anaxagoras'
even temperament was taken as a model of good behavior, and he was
famous as a prognosticator of everything from meteor falls to rain
showers. 




Anaxagoras' views appear among Socrates' survey of
previous naturalistic theories of explanation (*Phaedo* 96a6
ff.). More ominously, Meletus seems to have attributed Anaxagoras'
claims about the earthy nature of the moon and stars to Socrates at his
trial (see Plato's *Apology* 26e7ff., 59 A35). Although
Anaxagoras' alleged indictment for impiety was probably as much political
as a sign of his danger to public religion (attacking Anaxagoras was an
indirect attack on Pericles), he was seen as important and influential
enough to qualify to some as an enemy of the polis.




Philosophically, Anaxagoras' theories were also widely known and
influential. Some scholars have thought that the author of the Derveni
Papyrus (found in Northern Greece) was familiar with Anaxagoras'
theories (Betegh 2004; Kouremenos et al. 2006), and once he introduced
Mind as a cause, other thinkers followed him. Diogenes of Apollonia
claimed that air (as mind and god) directs all things. Zeno of Elea
(perhaps) and Melissus (certainly) criticize his theory. Anaxagoras'
view that "each one is and was most manifestly those things of
which there are the most in it" (the principle of Predominance)
is echoed in Plato's claims that sensible things acquire their
characters and names from the Forms in which they participate
(*Phaedo* 102a10 ff.). Plato even adopts Anaxagoras' language
of sharing or participating in (see Furley 2002), and like Anaxagoras' *nous*,
Platonic forms are "themselves by themselves" in being
self-explanatory (see Herrmann, 2007). Aristotle, although impatient
with the gaps in Anaxagoras' account of *nous*, expresses
admiration for his recognition that mind has a role to play in guiding
the cosmos, and he treats Anaxagoras' explanation of eclipses as a
model of scientific explanation.