## 1. Defining Renaissance Natural Philosophy



Renaissance natural philosophy defies easy definition, since
descriptions of it may oversimplify, either by reducing it to its
connections with medieval science or, alternatively, forcing it into a
teleology that culminates in the Scientific Revolution of the
seventeenth century. Hence, there have been two opposing tendencies in
scholarship: one which conflates the natural philosophy of the
fifteenth and sixteenth centuries with the variety practiced in the
Middle Ages, even going so far as to interpret the Renaissance as a
period of conservatism in this regard; another which emphasizes the
role of Renaissance natural philosophy as a "precursor" of
modern science, even at the cost of ignoring or removing its
connections to disciplines today considered pseudo-scientific, such as
physiognomy, astrology, and magic. Recent contributions, however, have
helped to outline the characteristics of Renaissance natural
philosophy in their own terms. Medieval natural philosophy was usually
based in the *corpus aristotelicum* and practiced in
universities. Yet this did not mean that its approach was purely
static or regressive; on the contrary, thinkers like Jean Buridan,
Biagio Pelacani, and Nicole Oresme took Aristotelian physics and
mechanics in new directions in medieval Europe. Nevertheless, the
nature of medieval universities was such that teaching was heavily
controlled by authorities, and especially outside of Italy both
metaphysics and theology exercised a strong influence. This imposed
some limitation to the directions in which scientific theorization
could advance. Paradoxically, it was the return of another, rival
school of thought--Platonism--that ultimately allowed for
more freedom within the Aristotelian tradition. Though Plato's
philosophy had never completely disappeared during the course of the
Middle Ages, the consolidation of a Neoplatonic school in the
fifteenth century led to the clear distinctions between the spheres
which properly belonged to the two great thinkers of the ancient
world. While Plato was regarded as a theologian and master of the
metaphysical realities, Aristotle was seen as an investigator of the
sublunar world subject to generation and corruption. The recovery of
this ancient dichotomy had the effect of undermining the longstanding
ties between Aristotelianism and Scholasticism, and opened up new
spaces for philosophy unimpaired by metaphysical limitations.
Moreover, an open dialogue with the Platonic tradition, caused several
professors to question Aristotle's coherence and reliability. At
the same time, also Platonism and other brands of ancient
philosophy--Stoicism, Skepticism, and
Epicureanism--stimulated reflection on the natural world in
different ways, also in terms of method. The application of these
ideas to various fields of inquiry gave Renaissance natural thought a
distinctive identity, forged in continuous dialectic with
Aristotelianism itself. Aristotelianism therefore represented the
driving force behind Renaissance philosophy of nature, both because of
its plurality of approaches and internal debates, and also because it
served as the polemical target of those who challenged the traditional
paradigm of university teaching: both followers and adversaries of
Aristotle had constantly to negotiate with his authoritative legacy,
and manipulate it. Finally, other factors of a non-speculative
character also had an impact on natural philosophy: technological
innovations such as printing, the telescope and the microscope,
geographical discoveries, and developments within the universities
themselves, such as the institution of botanical gardens.


## 2. Natural Philosophy and the *Curriculum*


### 2.1 Universities and Textbooks



The Aristotelian natural *corpus* covered a wide range of
subjects in a number of separate texts: while the *Physics* was
a sort of general work--which appeared to some fifteenth- and
sixteenth-century authors more metaphysical, even overlapping with the
*Metaphysics*--the other treatises represented different
sections of natural philosophy on particulars. The success and
influence of Aristotelian natural philosophy was due to its centrality
to university teaching, where it was favored because it covered every
topic, like an encyclopedia. Few attempts were made to reconsider
which texts represented the core of the study of natural philosophy in
the universities; one remarkable exception was Pierre de la
Ramee (1515-1572), who put a distinctive emphasis on
particular sciences at the expense of study of the *Physics*.
*Physics*, along with *On the Heavens, Meteorology,* and
*On Generation and Corruption*, was the main reference for
natural philosophy in the traditional *curricula* of the
Faculty of Arts. Universities--especially in
Italy--appointed many lecturers in natural philosophy, who
usually received high salaries. In the second half of the sixteenth
century, separate chairs of botany, mathematics, and even chemistry
(in Mantua and Germany), were established. Aristotelian texts were
traditionally studied according to the commentaries by Averroes (which
provided the internal partition of the texts into sections).



Between the fifteenth and sixteenth centuries, the works of other,
more ancient commentators on Aristotle were also adopted: those of
Alexander of Aphrodisias and Simplicius were particularly popular, the
first because of its radical mortalism, the second for its Neoplatonic
and conciliatory tendencies. The rediscovery of the ancient
commentators was accompanied by an increasing reliance on the Greek
texts in universities, despite the enduring predominance of medieval
Latin material. New commentaries also appeared alongside the ancient
ones: practically all of the most prominent professors composed their
own commentaries to the Aristotelian natural texts, in particular
between the sixteenth and seventeenth centuries. Usually these
commentaries followed the texts according to the Averroistic
divisions, but sometimes they were organized in
*quaestiones*.



Furthermore, the advent of printing made a large selection of
textbooks more widely available: some of them were very short
introductions for younger students, others were *compendia*,
others paraphrases (like those by Jacques Lefevre
d'Etaples (1455-1536), printed for the first time in
1492), and still others dialogues (again, Lefevre
d'Etaples created some of the most significant examples). Other
popular works used for teaching were abridged versions of the
Aristotelian treatises reduced to *conclusiones*, like the
popular *Textus abbreviatus philosophiae naturalis* by the
French theologian Thomas Bricot (d. 1516). There were also many
different textbooks, which generally followed canonical organizations:
either they explained the Aristotelian works according to their order
in the *corpus*, or they highlighted subjects like principles,
causes, movement, infinity, place, void, and time. The famous
*Commentarii Conimbricenses*, which from 1594 on became the
standard text in the Jesuit *curriculum,* contains a whole
course on natural philosophy organized as a commentary of the
Aristotelian corpus. Particularly after the second half of the
sixteenth century, vernacular treatments of Aristotelian natural
philosophy also began to circulate, such as the translations by
Antonio Brucioli (1498-1566), the paraphrases by Alessandro
Piccolomini (1508-1579), the summaries by Jean de Champaignac
(fl. 1595) and Scipion Dupleix (1569-1661), and the works by
Cesare Crivellati (1553-1640), the latter explicitly addressed
to university students.


### 2.2 Natural Philosophy's Rivalries and Interactions



Natural philosophy interacted with many other disciplines. The close
relationship between natural philosophy and medicine had already been
stressed by Aristotle himself at the beginning of *On Sense and
Sensible* (436a19-436b2). Medicine often competed with
natural philosophy within the universities: philosophy was a
curricular requirement for those who wanted to study medicine in the
Italian universities and many of the greatest Renaissance natural
philosophers were also physicians (e.g., Alessandro Achillini
(1463-1512) and Simone Porzio (1496-1554); there were also
professional physicians who wrote on natural philosophy, such as
Balthassar Pisanellus (fl. 1559) and Daniel Furlanus (d. 1600)).
*Ubi desinit philosophus* (or *physicus*), *incipit
medicus* ("where the philosopher ends, the physician
begins"): so went a proverb which implied an ambiguous boundary
between the two disciplines: on the one hand, it reflected the need to
move beyond the theory represented by philosophy and into the actual
practice of medicine; on the other, it affirmed the idea that natural
philosophy was necessary in order to prepare for medical studies. From
this perspective, natural philosophy represented either a mere
preparatory stage on the way to the more perfect and concrete
knowledge of medicine, or, alternatively, medicine was subordinate to
natural philosophy (others, like the philosopher Jacopo Zabarella
(1533-1589), preferred to distinguish natural philosophy from
medicine because these two disciplines did not share subject and
method).



The Renaissance debate over the superiority of Aristotle or Galen was
part of this rivalry: Aristotle was regarded by physicians as an
important authority because of his philosophical system, but Galen had
offered in his works more precise observations of the human body.
Nonetheless, since many points of their disagreement (e.g., the
localization of the brain functions) were merely founded on
speculation, some doctors preferred to demonstrate the harmony between
Aristotle and Galen in order to overcome this impasse.



Another discipline often compared to natural philosophy was astrology.
The Jesuit Benito Pereira (1536-1610) stated that natural
philosophy is different from astrology because, among other reasons,
the former studies things *a priori*, the latter *a
posteriori*. Pereira also claimed that natural philosophy was not
capable of delineating its own sphere of inquiry, something which was
possible for other disciplines such as logic and metaphysics.



University courses on the *Physics* traditionally began with a
lecture on ethical themes. This arrangement was inspired by
Averroes' proem to the text, which argued for the moral
perfection of the speculative man. The connection between ethics and
natural philosophy also appeared in discussions of subjects like the
immortality of the soul or the human will, and consequently ethical
discussions could occupy large sections both in *reportationes*
of lessons and commentaries.


## 3. Revising the *Curriculum*: Academies, Philology, and Botanical Gardens



Outside of universities and schools, there were also other places
where natural philosophy was cultivated, particularly in academies and
learned societies. Even in literary societies such as the
*Accademia Fiorentina* (1541), patronized by Duke Cosimo
de'Medici and his descendants, scientific matters (e.g., alchemy
or spontaneous generation) were occasionally debated, often in the
context of commentaries on the poems of Dante and Petrarch. The
*Accademia dei Lincei*, founded in 1603, on the other hand, was
exclusively interested in the sciences: as their statute dictated, the
*Lincei* had no interest in any controversy which was not
scientific or mathematical, and they avoided involvement in political
matters. The *Accademia dei Lincei*, like the *Accademia del
Cimento* after it (1657), was founded and patronized by members of
the aristocracy, but never became as well-grounded as other learned
societies, such as the Royal Society (1661) or the *Academie
Royale* (1666), which were directly sponsored by the state (the
*Academie Royale* even received financial support from
the treasury). Both of these latter institutions developed out of more
informal associations and they encouraged collaboration among their
members; they also explicitly endorsed the open and public exchange of
ideas, as opposed to the secretive practices of groups like the
*Lincei*. Their members gave public demonstrations of their
work, and the secrecy which had characterized scientific pursuit for
centuries was eventually abandoned in favor of a new empirical
approach.



Nonetheless, even when they did not sponsor academies, Renaissance
lords and patrons often had a particular interest in scientific works
and treatises, especially those devoted to subjects of military value
(such as the works on metalworking by Vannoccio Biringuccio and George
Agricola, or Niccolo Tartaglia's treatise on ballistics,
in the mid-sixteenth century), or booklets dedicated to *parva
naturalia*, which were intended as forms of intellectual
entertainment and usually contained descriptions of *miranda
naturae* or astrological predictions. Exceptional natural events
such as earthquakes--a famous one occurred in Pozzuoli in
1537--led to the publication of a number of short treatises that
interpreted the calamity as either a natural phenomenon or as a sign
sent by the celestial influences: these works were particularly sought
after by powerful men, who wanted to be reassured about the
significance of natural events and their possible consequences.
Several Renaissance rulers cultivated an interest in sciences like
alchemy, and patronized or participated first-hand in investigations
of the natural world: disciplines like zoology, which depended on the
collection of material, information, and drawings, relied particularly
heavily on the sponsorship of the wealthy and powerful. The zoological
and botanical works and catalogues which, though composed by
university professors, started from the 1540s to circulate around
Europe, were often addressed to or sponsored by rulers, who had the
means to employ artists and other specialists needed to complete these
costly volumes. Drawings were not simply ornaments to a text, but a
necessity for accurate classification of plants and animals.



The same desire for accuracy that motivated the production of
scientific images also led to more rigorous editions and translations
of classic scientific texts, whose impact was magnified by the
printing press. Between 1495 and 1498 Aldus Manutius printed the
"Greek Aristotle" in Venice, an edition prepared by a team
which included the humanist-physicians Niccolo Leoniceno and
Thomas Linacre under the guidance of another physician, Francesco
Cavalli. Consequently, Manutius's edition, which incorporated
significant improvements of the Aristotelian texts such as those
proposed years before by Theodor Gaza for the *Historia
Animalium*, favored the scientific works by Aristotle and did not
include, for example, either *Rhetoric* or *Poetics*.
Yet the scientific text that received the most attention from
philologists was Pliny's *Natural History*. Between the
fifteenth and sixteenth centuries Pliny's work was emended by
philologists such as Ermolao Barbaro, Angelo Poliziano, and
Niccolo Leoniceno--and also translated several times in
the vernaculars--in increasingly sophisticated versions. Both the
editions and the translations were intended to allow for a correct
understanding of the text, which was often used by doctors and
apothecaries. The same thing happened with Dioscorides'
*Materia medica*, a text that unlike the encyclopedic
*Natural History* was plainly addressed to a medical audience,
and which was then repeatedly emended and translated by professional
physicians and natural philosophers. Yet, also authors like Virgil,
Horace and Ovid were common presences in discussions about botany, and
even a philological evaluation of the text of the *Bible* could
provide material to natural philosophers.



The foundation of botanical gardens in Pisa, Padua, and Florence
(1544-1545), and then in Bologna, Leiden, Oxford, Montpellier,
and Germany testify to the fact that empirical knowledge was
increasingly considered a necessity even in the universities, despite
the fact that even at the end of the sixteenth century chairs in
botany, such as the one occupied by Andrea Cesalpino (1519-1603)
in Pisa, came with lower salaries than the ones given to their
"speculative colleagues" who taught natural philosophy or
medicine. The aforementioned catalogues of animals and plants, like
those published by Pierre Belon (1517-1564), Guillaume Rondelet
(1507-1566), and Ulisse Aldrovandi (1522-1605), were thus
a combination of received authority and empirical observation, based
on 1) a philological and critical knowledge of the classical texts,
not a passive reading of them; and 2) direct observations and
conversations not only with erudite peers and colleagues, but also
with the so-called "invisible
technicians"--fishermen, sailors, and peasants who had
first-hand knowledge of the relevant subjects and provided scientists
with important pieces of information. Not by chance, in a
little-explored field like the study of minerals, the most significant
contributions came from self-described "men without
letters" (meaning not Latinate), such as Leonardo da Vinci
(1452-1519) and the potter Bernard Palissy (1510-1589),
who identified fossils as the result of organic processes rather than
abstract virtues.



These empirical approaches were also stimulated by the European
discovery of the Americas and other continents, which contained plants
and animals never known or never described by classical authorities
like Aristotle and Pliny. The new knowledge brought by travelers and
explorers helped debunk erroneous doctrines advocated by Aristotle,
such as the uninhabitability of the torrid zone from
*Meteorology* 362b 6-9: a major exponent of Renaissance
Aristotelianism, Pietro Pomponazzi (1462-1525), publicly mocked
the Philosopher during his classes when discussing this passage, and
supported his position by referring to the direct, recent observations
of the navigator Antonio Pigafetta.



The shift from a text-based approach to the study of nature founded on
the study of a limited number of authors, to a new one based on an
enlarged encyclopedia and, above all, direct observation, reached its
full expression at the time of Galileo Galilei; but it was already
perceptible in the writings of Lorenzo Valla (circa
1406-1457)--who appealed to common sense against the
absurdity of some of the Aristotelian tenets--and in those of
Leonardo da Vinci, who invoked a virtuous interaction between science
and practice. When Tommaso Campanella (1568-1639) stated that he
learned more from the anatomy of an ant or an herb than from any book
ever written, he was simply expressing in a beautiful and poetic form
a shared methodological creed.


## 4. Aristotelian Tenets, Platonic Tenets, and More



The principal tenets of the Aristotelian natural philosophy were: the
doctrine of form and matter, the four causes, the rigid separation of
the world into opposed spheres, and the finite nature of the universe.
During the Renaissance, these precepts were both defended and revised
by Aristotelian professors, or challenged by others who sought to
dismantle traditional philosophy. While these new philosophers could
rely on new evidence, methods, and observations to define the nature
of the universe, in other cases the rejection of Aristotelian
doctrines and their substitution with new paradigms was mainly based
on speculative arguments. 


### 4.1 Principles and Matter


#### 4.1.1 Principles



According to Aristotle, if the sublunar world was characterized by
mutability, the supralunar world was--on the
contrary--absolutely immutable. The fundamental principles of
Aristotelian physics were in fact matter, form, and privation, and the
natural sublunar world was therefore the location where according to
these principles generation and corruption took place. Independent
philosophers offered alternatives to these principles and to the
Aristotelian hylemorphic apparatus. In order to describe nature within
its own limits, Bernardino Telesio (1509-1588)--a staunch
opponent of Aristotelianism--defended a different set of
principles which had already been proposed by authors such Girolamo
Cardano (1501-1576) and Girolamo Fracastoro (circa
1476-1553), and which he argued was based on data gathered from
experience rather than on arbitrary constructions. These alternative
principles were passive matter and active force, the latter
distinguished into heat and cold. It was the interplay--or
rather, the battle--between these opposite forces that brought
about the natural world. Since every natural being depends on the
interaction between cold and heat, it must know what is necessary for
its survival: therefore everything, including the forces themselves,
possesses sensation, which was not related to the faculties of the
soul, as in Aristotelian psychology. This connection between
*sensus* and self-preservation was also advocated by Tommaso
Campanella, who emphasized its importance for natural magic.
Telesio's polemical refusal of Aristotle and his call for
physical inquiry made within natural limits was appreciated and
praised even by those who recognized the contradictions in his
theories. Francesco Patrizi (1529-1597), who attacked Aristotle
from a Platonic perspective in his *Nova de Universis
Philosophia* (1591), rebuked Telesio for the latter's claim
to have relied exclusively on the senses and rejected reason: he
pointed out that, in reality, Telesio did rely on metaphysical
arguments, though he claimed to deny them (for his part, Patrizi
believed that natural philosophy requires metaphysical tools to fill
in its gaps). The same recognition of too much reliance on metaphysics
drove Francis Bacon (1561-1626) to reject Telesio's views
in favor of experimental empiricism and of a full endorsement of the
testimony of sensory perception.


#### 4.1.2 The Nature of Matter



Most Aristotelian interpreters believed matter to be *prope
nihil*, pure potentiality, while others believed that it possessed
a certain degree of reality and actuality. The discussion on the
nature of matter was further complicated by the suggestions offered by
other traditions of thought, Platonism above all. According to
Marsilio Ficino (1433-1499) in his *Platonic Theology*,
prime matter had an existence which is not dependent upon form.
Closely following the *Timaeus*, he claimed that matter can
therefore be intelligible, though in a weaker way. Giordano Bruno
(1548-1600) proposed an even more radical departure from
traditional views of the passivity of matter. In the *De la causa,
principio et uno*, Bruno affirmed that matter is an active
principle, not passive. Matter contains within itself every form, both
corporeal and incorporeal, and can be described as a kind of infinite
life. Bruno's conception of matter also served as the basis for
his cosmological views (see below), and in particular for his claim
that the universe is infinite. A few years later, Tommaso Campanella
returned to a more traditional position. In the *Del senso delle
cose e della magia* (printed in 1620) he argued for the synonymity
between matter and body, and against the identification of matter with
the Aristotelian *prope nihil*, though he did emphasize its
passivity: matter receives forms from external agents and does not
produce them from within itself.



Closely related to these problems was Aristotle's doctrine of
prime matter, which had controversial implications: as matter was
eternal, so was the world, and therefore the Christian dogma of the
creation of the world was untenable. Scholastic philosophers had long
struggled with this subject during the Middle Ages, and the most
interesting developments during the Renaissance were driven by the
confrontation between Aristotelianism and Platonism. Plato, in the
*Timaeus*, had clearly spoken of a God-creator, and once again
his doctrines were adopted by authors anxious to establish a new
philosophical foundation for Christianity. Bessarion (d. 1472), for
example, admitted that according to Plato matter was eternal, but that
he distinguished it clearly from the creator, who possesses a superior
eternity. In similar fashion, Marsilio Ficino expressly described
prime matter as created and therefore not subject to generation and
corruption. Aristotelians were not always afraid, however, to argue
for the eternity of the prime matter: Francesco Vimercato
(1512-1569), in his posthumous *De rerum principiis*, is
the most remarkable example. As late as the beginning of the
seventeenth century, the debate continued: Cesare Crivellati composed
a dialogue (1617) between Plato and Aristotle in which the master
rebukes his unfaithful student for teaching such an impious doctrine.
On the other hand, there were also authors who attempted to establish
an accord between Plato and Aristotle on this sensitive issue: a good
example is the *De naturae philosophia seu de Platonis et
Aristotelis consensione* (1554) by Sebastian Fox Morcillo
(1526-1560), in which the Spanish philosopher compares the
doctrines of the *Timaeus* and the *Physics*, and
emphasizes the limits of both in front of the perfection of
religion.



Other thinkers instead had a pragmatic approach to prime matter:
alchemists like the Swiss physician Paracelsus (1493-1541)
sought to find a principle to which every substance could be reduced.
Though openly challenging traditional university teaching, Paracelsus
did not reject canonical motifs. For example, he relied on the four
elements (air, fire, water, earth), but he also proposed a new triad:
sulfur, mercury, and salt. Yet, even this proposal was not as
iconoclastic as it appears, since it was partially founded on the
Aristotelian doctrine of the formation of metals contained in the
*Meteorology* (341b 6ff.). Nonetheless, by emphasizing the
processes of association and dissociation of substances, Paracelsus
offered an important contribution to the transformation of alchemy
into chemistry (even if the two terms were often intended as
interchangeable). Gradually chemistry separated from physics,
understood as the science of bodies subject to movement, and
positioned itself as the science of bodies associated and dissociated.
Johann Baptist Van Helmont (1579-1644), who opposed the
Paracelsian principles, developed a corpuscular doctrine of matter, a
variant of atomistic theory. Atomism in the Renaissance was typically
related to the Neoplatonic concept of *semina* and to the
Epicurean philosophy, and was usually advocated by radical
anti-Aristotelian thinkers like Giordano Bruno. And while it is true
that Aristotle rejected atomism and the existence of the void, there
were ways to argue for a Peripatetic version of atomism.






Some medieval philosophers admitted the existence of *minima
naturalia*, the limits beyond which form is not conserved. The
doctrine of the *minima* was intended to resolve a problem
raised by Aristotle in *On Generation and Corruption* (327a
30-328b 24), namely, that of the necessity of finding a
philosophical justification for combination, an intermediate
phenomenon between generation and corruption. Over the course of the
Renaissance the doctrine of *minima naturalia* was further
elaborated by authors like Agostino Nifo (circa 1469-circa 1539)
and Julius Caesar Scaliger (1484-1558). Scaliger granted a
consistency to the *minima*, making them not mere limits, but
real physical components that cannot be further divided. Furthermore,
he rejected traditional atomism, because it did not achieve the
continuity of the corpuscles which constitute a body. Despite their
opposition to Peripateticism, the corpuscularism of Van Helmont and
Daniel Sennert (1572-1637) was rooted in this tradition.
Sennert, in particular, was unable to reject the Aristotelian concept
of form, and aimed instead to establish a concord between
Aristotelianism and atomism. Even in a work programmatically entitled
*Philosophia Naturalis adversus Aristotelem* (1621), Sebastian
Basson--who defended corpuscularism--denied the existence of
the void and rejected a mechanization of the natural world. It was
Galileo Galilei who made a bold departure from the qualitative
background of Aristotelian matter, defending a mechanistic form of
atomism in which atoms did not have dimensions. Despite the attempts
of Pierre Gassendi (1592-1655) to conciliate it with
Christianity, atomism bothered traditionalists also for its
theological implications, both large (the teleological vision of the
world) and small (transubstantiation). Even Rene Descartes
(1596-1650) came under attack for this reason. Debate over the
existence of the void was also lively throughout the seventeenth
century, largely because of the experimental work of Evangelista
Torricelli (1608-1647), Valeriano Magni (1586-1661), Otto
Von Guericke (1602-1686), and Robert Boyle (1627-1691),
who opposed the traditional views of the so-called
"plenists". 


### 4.2 Old Cosmologies, New Cosmologies



The rigid peripatetic division of the universe into two different
parts--one immutable and made of crystalline spheres, situated
between the fixed stars and the moon, the other mutable, under the
moon--was also related in the Aristotelian paradigm to the
concept of the natural sublunar world formed by the four elements:
fire, air, water, and earth. Every element behaves differently,
according to its so-called "natural movement". Light
elements, such as fire and air, always tend to go upward, while heavy
elements, such as water and earth, move downward following a
rectilinear movement. Every element aims, in fact, to reach its own
natural place, unless an external force causes a movement opposite to
its nature--a "violent movement" (e.g., a stone
thrown into the air). In both cases, Aristotelian theory considers
movement as a quality common to all natural things because of the
elements which compose them. By contrast, the heavens, since perfect
and composed by a single element (aether), are immutable and travel in
constant circular motion around an immovable center represented by
Earth. An important corollary to the theory of natural places was the
finite character of the world, because it implied the existence of a
unique center (the Earth), while evidently it would not be possible
for an infinite universe to have a center.



These longstanding paradigms were destined to be challenged from the
sixteenth century onward, both from a speculative and an empirical
perspective. Observation of *stellae novae* and comets
condemned the crystalline spheres and raised doubts regarding the
doctrine of the immutability of heavens. According to the traditional
Aristotelian account, comets were phenomena in the sublunar
atmosphere. The great astronomer Johannes Regiomontanus
(1436-1476) did not challenge this vision of the cosmos when he
calculated the distance of the 1472 comet by considering the angle of
parallax, but about a century later, the Jesuit Christopher Clavius
(1538-1612), observing a *nova* (1572), and Tycho Brahe
(1546-1601), observing a comet (1577), both demonstrated that
the suddenly bright star and the comet must lie beyond the moon, and
that therefore the doctrine of the spheres was false. The demonstrated
fluidity of heavens also compromised, more crucially, the doctrine of
their immutability. Two factors made possible such an achievement: the
availability of better measuring instruments, and a stronger emphasis
on mathematics. This emphasis on mathematics was probably the most
important contribution of Platonism to the development of natural
philosophy, and in particular astronomy, during the Renaissance.
Though it is true that Neoplatonic philosophers had proposed
alternatives to the Peripatetic theories on the heavens (e.g.,
Marsilio Ficino argued that the heavens were made of *spiritus*
and rejected the division of the universe into spheres), it was their
insistence on the importance of geometry and mathematics that helped
opening the way to the quantitative vision of the world, which
gradually replaced the qualitative paradigm connected to the
Aristotelian tradition.



The decision of Nicolaus Copernicus (1473-1543) to propose a
heliocentric system, remove the Earth from the center of the universe,
and establish a relationship between the distances of the different
planets from the sun and the amplitude of their orbits was based on
mathematical reasoning and the weaknesses of Aristotelian-Ptolemaic
system in this regard. Johannes Kepler (1571-1630) defended the
Copernican theory by re-utilizing geometrical arguments from
Plato's *Timaeus*, and he also developed other theories
(such as the elliptical form of the planetary orbits) founded on the
geometrical structure that he attributed to the universe. Despite the
fact that aspects of his method, and in particular the
*regressus,* were essentially Aristotelian, Galileo Galilei
(1564-1642) has been often described as a Platonist, insofar as
Platonism endorsed a mathematical approach. Galileo denied the reality
of the physical elements of the Aristotelian world and the theory of
their natural movements, and replaced them with corporeal matter,
whose properties and motions could be described in mathematical terms.
Furthermore, by relying on new instruments such as the telescope,
Galileo was also able to make new observations which revealed the
imperfections of the supralunar world. Galileo and the Copernican
theory met with the resistance of the Church, but also of the
universities, whose professoriate was not eager to renounce one of the
central pillars of its teaching. On the other hand, the Tychonic
system elaborated by Brahe, which attempted to conciliate the
traditional Aristotelian-Ptolemaic cosmology with Copernicus,
encountered support even among Jesuit scientists.



However, neither mathematics nor fresh observations were capable of
resolving the problem of the nature of the universe: was it finite or
infinite? Is there only one world or do multiple worlds exist?
According to the Aristotelians the universe must be finite, because it
is impossible to have an infinite body in act, and Copernicus and his
followers also endorsed the finitude of the heavens. Theology,
however, offered arguments against the finitude of the universe:
Nicholas of Cusa (1401-1464) connected the infinity of God to
the infinity of heavens, and Palingenio Stellato (or Pierangelo
Manzolli, 1500/3-1543 ca.), in his *Zodiacus Vitae*,
compiled themes from different traditions (e.g., the Aristotelian
spheres and the Platonic ideas), describing a universe made of
infinite light in order to celebrate the glory of God. Francisco
Suarez (1548-1617), and a few years later the
*Conimbricenses*, also defended the existence of an infinite
space, even if it was only an imaginary one, combining Peripatetic
doctrines with theological ones (above all the omnipresence of God,
which cannot be limited by a finite space). Giordano Bruno used the
relationship between God and His creation to argue for the infinity of
the world. Bruno's position was in complete opposition to the
Aristotelian cosmology: the spheres are broken, there is no hierarchy
between the different parts of the world and no center, and therefore
the natural movements are rejected. Bruno developed his theory of
infinity not only by relying on metaphysical arguments, but also on a
radical revision of the Aristotelian definition of space, which he
understood as a continuous quantity. Bruno's proposal provoked
reactions all over Europe: Kepler rejected it several times in
different ways. Nevertheless, Kepler agreed with Bruno's belief
in the plurality of worlds--a problem which raised theological
issues because of the question of salvation. Tommaso
Campanella--an author who denied the infinity of the
universe--resolved it by arguing that the inhabitants of the
other worlds were not men, and therefore did not need to be saved by
God.


### 4.3 Miracles, Magic, and Physiognomy



In the Middle Ages authors like Pietro of Abano, Nicolas Oresme, and
John Buridan argued that any phenomenon, in particular those which
were usually believed to be supernatural or miraculous, could be
explained according to natural principles as the result of hidden
causes. A number of Renaissance thinkers also adopted this approach,
including Pietro Pomponazzi. In his *De incantationibus*,
Pomponazzi stated that men tend to consider phenomena wondrous when
they are not able to identify their causes as the work of demons or
miracles. Pomponazzi attributed apparently miraculous events to the
power of imagination, to psychological states or to the influence of
the stars, since according to the Peripatetic paradigm the immutable
first mover cannot have direct contact with the mutable sublunar
world, and therefore moves through secondary causes. Nonetheless,
despite his claim to speak purely *secundum Aristotelem*,
Pomponazzi relied on a wider range of readings, including Marsilio
Ficino. And in making these claims, Pomponazzi encroaches on very
sensitive questions of religious faith. In his view, Christian
miracles can be understood in the context of a sort of philosophy of
history, founded on the horoscope of religions: when a religion
begins, miracles occur, which are caused by starry influences, and
when a religion declines, miracles disappear, because starry
influences are weaker. This paradigm involved a rigid organization of
the universe, which left little or no space for free will. Pomponazzi
took this doctrine to its logical extreme in his *De fato*, a
work in which he claimed to endorse Stoicism, while in reality
exposing the determinism embedded in the Aristotelian doctrine of
causes. Other Aristotelians who sought to avoid this determinism
usually relied on the moderate position of Alexander of Aphrodisias,
who Pomponazzi attacked in the first part of his treatise. While
Pomponazzi reached these conclusions drawing on multiple sources,
other authors, such as Gerardus Bucoldianus, Simone Porzio, and
Ludovico Boccadiferro preferred to rely solely on Aristotle in order
to explain wondrous events like cataclysms or the appearance of
monstrous creatures, like those described by Ulisse Aldrovandi
(1522-1605), who interpreted them as deviations from the course
of nature, or Fortunio Liceti (1577-1657), who preferred to link
the appearance of monsters to ingenious experiments of nature.



Nevertheless, this approach, which reduced the supernatural to the
natural, was not always coupled with Aristotelianism. On the contrary,
it was often directed against Peripatetic doctrines, particularly when
it relied on experimental and empirical observations. The search for
the occult causes of things, which was often related to magical
beliefs and practices, effectively stimulated new empirical
approaches: Giovanbattista della Porta (1535-1615) was among
those who offered natural explanations for exceptional events while
discarding the Aristotelian paradigm in favor of direct experience, in
works such as the *Magiae naturalis sive de miraculis rerum
naturalium*. Della Porta insisted on the sympathy and the
antipathy of things, which are influenced by celestial virtues, when
dealing with topics like optics and magnetism. And the *De
magnete* of the anti-Aristotelian William Gilbert
(1544-1603) mixed experimentation (aimed at the demonstration of
the rotation and the magnetism of earth) with the belief in the
existence of a soul belonging to the earth. The occult properties of
things were also explored by other disciplines, such as medicine. Jean
Fernel (1497-1558) and Girolamo Fracastoro argued that occult
properties could be used to explain diseases and contagions.



The knowledge of the secrets of nature was in fact central to magic, a
field which had an ambiguous relationship to natural philosophy. If a
natural philosopher wanted to describe and understand nature, a
practitioner of magic wanted to investigate it and its occult
properties in order to master it. The Neoplatonic correspondences
between *macrocosmus*--the world--and
*microcosmus*--man--allow magic to exercise its power
on a reality which was seen in vitalistic and transcendental terms:
the book of nature for practitioners of magic was not the same one as
that of the Aristotelians or of Galileo, but it was written with signs
and allusions. Magical doctrines had a wide circulation throughout the
Middle Ages, but were enriched in the fifteenth century by the
rediscovery of the *Corpus Hermeticum*. The *Corpus* was
a collection of heterogeneous texts, dealing both with practical magic
and the mystical teachings attributed to Hermes Trismegistus, an
Egyptian sage who purportedly lived at the time of Moses and was first
in the lineage of a tradition of wisdom (the so-called *prisca
theologia*). The alleged antiquity of the *Corpus*
represented the strongest evidence of its authority and reliability,
and thinkers like Marsilio Ficino in his *De vita,* and then
Cornelius Agrippa (1486-1535) in his *De occulta
philosophia*, proposed doctrines based on it. Their readers were
encouraged to carve talismans and images, and surround themselves with
precise colors or herbs connected to planetary influences in order to
exploit the conjunction of the whole, a living being of which man is
both part and lord. Magical treatises included recipes and empirical
descriptions, and in his *De augmentis Scientiarum* even
Francis Bacon described magic as an operative knowledge of hidden
forms and the harmony of things, which displays the wonderful works of
nature. The connection between *micro* and *macrocosmus*
also underlay medical practice--as in the case of Ficino himself
and later Paracelsus--and disciplines like physiognomy, which was
considered part of the Aristotelian natural encyclopedia. Della
Porta's *De physiognomia humana* (1586), which was mainly
a collection of past authorities that included ethical problems and
was accompanied by illustrations, became the standard text on the
topic until Lavater. There were also expressly hermetic approaches to
the subject, including the one by Robert Fludd (1574-1637).


### 4.4 Natural Philosophy and Religion



Many of the doctrines of natural philosophy contrasted with the
teachings of religion, and there were a number of possible solutions
to this problem. Some authors appealed to the radical difference
between the realms of faith and philosophy, relying on the Averroistic
(even if not formulated by Averroes himself) doctrine of the
"double truth". This was the case, for example, of Pietro
Pomponazzi. Yet other authors, such as Bessarion or Simone Porzio, who
came from very different backgrounds, rejected any confusion between
philosophy and faith at the latter's expense (even though
Bessarion, like Ficino, argued for a greater compatibility between
Platonism and Christianity). There were also others, like the Jesuit
Pedro da Fonseca (1528-1599), who considered Plato's
natural philosophy too dangerously similar to Christianity and
therefore preferred the Aristotelian paradigm. On the other hand, some
thinkers tried instead to genuinely reconcile philosophy and faith,
particularly during the periods of doctrinal conflict and religious
warfare that followed the Reformation. This was particularly true in
Protestant countries, where even at the end of the sixteenth century
the problem of the double truth was a matter of intense debate.
Reformed scholars displayed a clear bias against Aristotle, the
philosopher who they held responsible for sustaining the scholastic
edifice of Catholic theology, and in Wittenberg they even mounted a
short-lived attempt to replace him with Pliny: but the disordered
approach of the *Natural History* made it unsuitable for
superseding the Aristotelian encyclopedia for teaching. Philipp
Melanchthon (1497-1560) reconciled the distinction between
religion and science of nature by arguing that nature was creation of
God and everything in it had to be seen as the work of providence.
Some philosophers, such as John Amos Comenius (1592-1670),
supported the alliance between natural science and religion by arguing
for a philosophy based on the biblical teachings, even though this
position was often intended to combat the excess of natural
philosophers rather than to offer an alternative system. However, both
in Protestant and Catholic contexts, scientists like Rheticus
(1514-1574) and Galileo denied that the Bible had any scientific
value (yet, refusing *tout court* the divine role in the
explanation of Biblical events such as the Genesis flood, in favor a
of a fully natural account, as Camilla Erculiani suggested in 1584,
was likely to cause the intervention of the Roman Inquisition).
Scholars like John Case (d. 1600), who considered Aristotelianism
compatible with Christian dogmas such as creation and divine
providence, were particularly fond of searching for ways to syncretize
theology with natural philosophy. Attempts to reconcile the
Philosopher with the Christian religion, even at the cost of relying
on forced or fanciful readings, were still being made in the
seventeenth century. Descartes will solve the interferences between
natural science and religion by limiting the former to the
investigation of finite objects, the only ones accessible to human
beings. Yet, by posing limits to human knowledge, he also rejected an
anthropocentric view of the creation.



Nor were these problems confined to Christian learned contexts: they
were the subject of a number of similar reflections within the Jewish
tradition as well. Jewish thinkers often considered natural science a
mere system of hypotheses, which was capable of grasping only the
superficial appearance of things, and was subordinate to the absolute
truth offered by the Torah. This position was defended by authors such
as Judah Loew ben Bezalel (also known as Maharal, 1520-1609),
who posited a radical distinction between the natural world and the
teachings of Torah, as well as Azariah Figo (1579-1547). In
particular, Loew claimed that while it was possible to illuminate and
explain the natural order of the physical world, this was not true of
the relationship between God and the creation. This attitude was
probably in part due to Jews' sense of exclusion and
marginalization from the institutions where natural philosophy was
taught and practiced (an important exception to this rule was Italy,
where personalities like Elijah del Medigo (circa 1458-1493)
took advantage of the separation between science and theology in the
universities). Nonetheless, all of these Jewish authors--both the
Italian "free-thinkers" and those who defended the
superiority of the Torah--still relied on Aristotle as the main
authority for natural philosophy, and there were multiple attempts by
philosophers like Ioseph ben Shem Tov (circa 1400-circa 1480)
and Abraham Farissol (1451-circa 1525) to integrate the
Stagirite within the Hebraic philosophical tradition. A minority of
Jewish authors, including Moses Isserles (1520-1572), considered
natural philosophy a useful tool for demonstrating the glory of God.