logical constants for correct inferences while informal logic also takes the meaning of substantive
concepts into account. Further approaches focus on the discussion of logical topics with or without formal
devices and on the role of epistemology for the assessment of arguments.[40]
Premises and conclusions are the basic parts of inferences or arguments and therefore play a central role
in logic. In the case of a valid inference or a correct argument, the conclusion follows from the premises,
or in other words, the premises support the conclusion.[41] For instance, the premises "Mars is red" and
"Mars is a planet" support the conclusion "Mars is a red planet". For most types of logic, it is accepted
that premises and conclusions have to be truth-bearers.[41][a] This means that they have a truth value: they
are either true or false. Contemporary philosophy generally sees them either as propositions or as
sentences.[43] Propositions are the denotations of sentences and are usually seen as abstract objects.[44]
For example, the English sentence "the tree is green" is different from the German sentence "der Baum ist
grün" but both express the same proposition.[45]
Propositional theories of premises and conclusions are often criticized because they rely on abstract
objects. For instance, philosophical naturalists usually reject the existence of abstract objects. Other
arguments concern the challenges involved in specifying the identity criteria of propositions.[43] These
objections are avoided by seeing premises and conclusions not as propositions but as sentences, i.e. as
concrete linguistic objects like the symbols displayed on a page of a book. But this approach comes with
new problems of its own: sentences are often context-dependent and ambiguous, meaning an argument's
validity would not only depend on its parts but also on its context and on how it is interpreted.[46] Another
approach is to understand premises and conclusions in psychological terms as thoughts or judgments.
This position is known as psychologism. It was discussed at length around the turn of the 20th century
but it is not widely accepted today.[47]
Premises and conclusions have an internal structure. As propositions or sentences, they can be either
simple or complex.[48] A complex proposition has other propositions as its constituents, which are linked
to each other through propositional connectives like "and" or "if...then". Simple propositions, on the other
hand, do not have propositional parts. But they can also be conceived as having an internal structure: they
are made up of subpropositional parts, like singular terms and predicates.[49][48] For example, the simple
proposition "Mars is red" can be formed by applying the predicate "red" to the singular term "Mars". In
contrast, the complex proposition "Mars is red and Venus is white" is made up of two simple propositions
connected by the propositional connective "and".[49]
Whether a proposition is true depends, at least in part, on its constituents. For complex propositions
formed using truth-functional propositional connectives, their truth only depends on the truth values of
their parts.[49][50] But this relation is more complicated in the case of simple propositions and their
Basic concepts
Premises, conclusions, and truth
Premises and conclusions
Internal structure