Philosophical Language

Philosophy, like all other academic disciplines, has its own terminology. This terminology can sometimes be confusing. Your best guide to using philosophical language properly is to keep careful notes and, when in doubt, look up the meaning of a term before you use it in a paper. Here you’ll find a very incomplete list of terminology that is used in a way that is peculiar to philosophy. This page will be subject to additions and refinements.

For a much more comprehensive survey of philosophical language, consider purchasing The Penguin Dictionary of Philosophy.


ARGUMENT: A set of propo­si­tions, one of which is the con­clu­sion and the rest of which are the premis­es.

BELIEF: A men­tal state that rep­re­sents the world as being a cer­tain way.

  • Belief Con­tent: The con­tent of a belief is a propo­si­tion about the way things are. One believes that [propo­si­tion], e.g., one believes that cof­fee is tasty.
  • True/False Belief: When that rep­re­sen­ta­tion is accu­rate, the belief is true and when it is inac­cu­rate it is false. When we speak of a true belief we are refer­ring to the truth val­ue of the propo­si­tion believed, i.e., whether it is true or false, not to the authen­tic­i­ty of the belief; both a true belief and a false belief are real beliefs.
  • Sig­nif­i­cance: In ordi­nary Eng­lish, we often use “belief” to refer to those pro­found com­mit­ments that are close to the core of our being; e.g., S believes in God, S does not believe in the death penal­ty. In phi­los­o­phy, even com­mon­place beliefs are the sub­ject of con­tro­ver­sy, so we use “belief” to refer to one’s belief that there is a desk in the room, that it is sun­ny out­side, that 5+7=12, etc. as well as one’s belief that God exists, that the death penal­ty is unjust, that there is no life after death, etc.

CONCLUSION: A propo­si­tion that is sup­posed to be sup­port­ed by premis­es.

KNOWLEDGE: Just what counts as knowl­edge is con­tro­ver­sial, but there are some things to which vir­tu­al­ly all philoso­phers agree.

  • Con­tent: Gen­er­al­ly, we are talk­ing about know­ing that a propo­si­tion is true when we speak of knowl­edge, i.e., propo­si­tion­al knowl­edge. There are oth­er kinds of knowl­edge, e.g., know­ing how to do some­thing or know-how, but those are spe­cial cas­es and philoso­phers will usu­al­ly make it clear if they are using “knowl­edge” to refer to some­thing oth­er than propo­si­tion­al knowledge.
  • Belief: Every instance of knowl­edge is also a belief but not all beliefs are instances of knowl­edge. Just imag­ine some­one who has nev­er thought about whether or not most den­tists wear hats. This per­son does not even believe that most den­tists wear hats, let alone know that most den­tists wear hats. So, belief is a nec­es­sary com­po­nent of knowledge.
  • Truth: Only true beliefs, i.e., beliefs that accu­rate­ly rep­re­sent the world, can amount to knowl­edge. Just imag­ine some­one who believes that most den­tists do not wear hats when, as a mat­ter of fact, most do. Even though this per­son has a belief, their belief is false so, although they might believe that they have knowl­edge, they’re wrong about that.
  • Jus­ti­fi­ca­tion: But even true beliefs are not enough for knowl­edge. Some­one who guess­es that most den­tists wear hats and hap­pens to be right about that doesn’t know that most den­tists wear hats; what’s miss­ing is evi­dence, rea­son to believe, or jus­ti­fi­ca­tion for the belief.
  • Know­ing & Know­ing that You Know: There is a dif­fer­ence between know­ing that some­thing is true and know­ing that you know that it is true. There might be inter­est­ing rela­tion­ships between the two, but they are at least con­cep­tu­al­ly dis­tinct. So, be care­ful not to con­fuse the ques­tion, “does S know that p?” with the ques­tion, “does S know that she knows that p?”

PREMISESPropo­si­tions that are sup­posed to sup­portcon­clu­sion.

PROPOSITION: The con­tent of a declar­a­tive sen­tence on a par­tic­u­lar occa­sion, in oth­er words, the sort of thing that can be true or false. A ques­tion does not express a propo­si­tion, since ques­tions can­not be true or false. Declar­a­tive sen­tences might express things oth­er than propo­si­tions, too. For exam­ple, if I say “Jere­my was late for class” I might express the propo­si­tion that Jere­my was late for class and also express my con­tempt for Jeremy.

SUPPORT: There is no uncon­tro­ver­sial char­ac­ter­i­za­tion of sup­port, but it can be thought of as a rela­tion­ship two or more propo­si­tions bear to each oth­er when the truth of some of them increas­es the like­li­hood of the truth of the oth­ers. For exam­ple, that the mur­der­er was left hand­ed and that Jere­my is left hand­ed con­joint­ly sup­port that Jere­my is the mur­der­er. They DO NOT prove that Jere­my is the mur­dered, but they increase the like­li­hood, if only a bit, that Jere­my is the murderer.

TRUTH VALUE: A propo­si­tion gen­er­al­ly has a truth-val­ue, i.e., it is either true or false. If a propo­si­tion is true, then it is said to have a truth-val­ue of true and when it is false, it is said to have a truth-val­ue of false. Not all sen­tences have a truth val­ue, e.g., ques­tions and com­mands have no truth-val­ue. Some propo­si­tions might not have truth-val­ues as well; Aris­to­tle believed that propo­si­tions about the future are some­times nei­ther true nor false, e.g., the propo­si­tion [There will be a sea bat­tle tomor­row] is nei­ther true nor false today, but will be either true or false tomor­row (and for­ev­er after).

VALID: If the con­clu­sion of an argu­ment must be true giv­en that the premis­es are true, then the argu­ment is valid. In oth­er words, the truth of the premis­es would guar­an­tee the truth of the con­clu­sion, rather than just mak­ing it like­ly. Only argu­ments can, strict­ly speak­ing, be valid; the­o­ries, claims, ideas, etc. can­not be valid or invalid.

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