Glossary of philosophical terms

(See also Jim Pryor’s page on Philosophical Terms and Methods.)

ambiguity The possession of two or more different meanings by a single word (type). Example: “bank” means both money-bank and river-bank.

antecedent The “if” part of a conditional: e.g., “Bush is president” in “If Bush is president, then he is over 35 years of age.”

a priori  Without appeal to experience (usually applied to knowledge).

ceteris paribus  other things being equal

conclusionThe sentence one is trying to establish in a piece of reasoning. See also inference, premises.

conditional An “if then” statement, e.g. “If Bush is president, then he is over 35 years of age.” See also antecedent and consequent.

contingent Neither necessary nor impossible.

conjunct One of the two sentences connected by “and” in a conjunction.

conjunction An “and” statement, e.g. “Berkeley is in California and Reno is in Nevada.” See also conjunct.

consequent The “then” part of a conditional: e.g., “[Bush] is over 35 years of age” in “If Bush is president, then he is over 35 years of age.”

disjunct One of the two sentences connected by “or” in a disjunction.

disjunction An “or” statement, e.g. “Figs are fruits or figs are vegetables.” See also disjunct.

elenchus  Socrates’ method of “examination” or “refutation,” in which a claim is refuted by showing it to be inconsistent with other beliefs held by the person who makes it.  

epistemology  Branch of philosophy concerned with knowledge and justification.

extensionally equivalent  Two predicates (or concepts) are extensionally equivalent iff they are true of exactly the same objects.  Classic example:  “is a creature with a heart,”  “is a creature with a kidney.”

ex hypothesi  by hypothesis

iff  if and only if

inference A piece of reasoning consisting of one or more premises and a conclusion. See also valid.

lex talionis  Law of retaliation.  

materially equivalent  “A is materially equivalent to B” means “A if and only if B.” 

modal  Having to do with necessity and possibility.

mutatis mutandis  Latin phrase meaning “the things that are to be changed having been changed,” i.e., “when the relevant changes have been made.”

necessary condition A is a necessary condition for B just in case B can’t be true unless A is also true: that is, if B, then A.

p  Generally a placeholder for an unspecified sentence.

premises Sentences that form the basis for a piece of reasoning; the premises in an inference are supposed to support the conclusion. 

sound  An inference is sound just in case it is valid and all of its premises are true.

sufficient condition A is a sufficient condition for B just in case A’s truth guarantees B’s truth: that is, if A, then B.

token An instance of a type.  

type A kind of thing that can have multiple tokens or instances.  For example, there are six different letter-tokens, but only two different letter-types, in the following sequence:  ABBBAA.  

valid  An inference is valid just in case it is impossible for all the premises to be true and the conclusion false. Note: an inference can be valid even if it’s conclusion is false. See also sound, inference, argument.