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?”
PREMISES: Propositions that are supposed to support a conclusion.
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.