In this piece I will explain why philosophical terminology is important and I will present definitions for twenty important philosophical terms I think can help improve our thinking about various philosophical issues.
Why are philosophical terms important?
Language helps us think. Without language it would be a lot more difficult (or perhaps impossible) to understand what subatomic particles are, to be able to consider what the ultimate form of reality is, or to consider what theory of justification is best. Words and terms are some of the most important parts of language and can be very helpful tools for improving our thought.
Philosophical language (or jargon) has a lot to offer. Philosophers spend a lot of time making new distinctions and they find it both convenient and sometimes indispensable to use their specialized jargon. For example, David Hume discussed “matters of fact” (facts about the world known through observation/empirical evidence) and “relations of ideas” (things true by definition and known through understanding a language that do not help us understand the world itself). Hume thought all knowledge must consist of these two categories. Later Immanuel Kant realized that Hume assumed all knowledge was analytic a priori (nonempirical and true by definition) and synthetic a posteriori (empirical and not true by definition), but that made room for one more category. Kant thought there was a type of knowledge that Hume missed—the synthetic a priori (nonempirical knowledge that’s not true by definition). For example, Kant thought the truths of geometry could be known from a synthetic a priori justification.
Twenty important philosophical terms
a posteriori – Latin for “from the later.” A posteriori statements or beliefs are justified entirely by observation. (e.g. “Human beings are mammals.”) The opposite of a priori.
a priori – Latin for “from the earlier.” A priori statements or beliefs are justified (at least in part) by something other than observation. Many philosophers agree that things that are true by definition have an a priori justification. (e.g. “All bachelors are unmarried.”) The opposite of a posteriori.
analytic – Analytic statements or beliefs that are true because of their meaning. (e.g. “All bachelors are unmarried.”) The opposite of “synthetic.”
synthetic – Statements that cannot be true by definition. Instead, they can be true because of how they relate to something other than their meaning, such as how they relate to the world. For example, “humans are mammals” is synthetic and can be justified through empirical science. “Synthetic” is the opposite of “analytic.”
categorical imperative – An imperative is a command or requirement. Categorical imperatives are overriding commands or requirements that don’t depend on our desires, and are rational even if we’d rather do something else. For example, it is plausible that we have a categorical imperative not to run around punching everyone in the face just for entertainment. The mere fact that someone might want to do it does not make it morally acceptable. Categorical imperatives are often contrasted with “hypothetical imperatives.”
hypothetical imperative – Imperatives are commands or requirements. Hypothetical imperatives are those we are required to do in order to fulfill our desires or goals. For example, if you are hungry, then you have a hypothetical imperative to get some food to eat. “Hypothetical imperatives” are often contrasted with “categorical imperatives.”
coherentism – The view that we start with various assumptions and such assumptions are justified as long as they are part of a coherent world view (mutually supported by other beliefs). It is often claimed that an assumption is justified through coherence if it is useful as part of an explanation. Observation itself is meaningless without assumptions, and observation appears to confirm our assumptions as long as our observations are consistent with them. For example, my assumption that a table exists can be confirmed by touching the table. Some philosophers argue that coherentism should be rejected because it legitimizes “circular reasoning,” which we ordinarily recognize as being a fallacious form of justification.
foundationalism – The view that there are privileged or axiomatic foundational beliefs that need not be proven. The source of privileged beliefs could be from self-evidence, non-inferential reasoning, non-empirical intuitive evidence, or perhaps even beliefs based on certain experiences. Foundationalism is one possible solution to the problem of justification requiring an infinite regress or circular reasoning. If everything we know needs to be justified from an argument, then we need to prove our beliefs using arguments on and on forever, or we need to be able to justify beliefs with other beliefs in a circular mutually supportive fashion; but foundationalism requires us to reject that everything we know must be justified with an argument (or argument-like reasoning).
emergence – (1) Epistemic emergence refers to our inability to know how to reduce one phenomenon into another. For example, chemistry is epistemically emergent insofar as we don’t know how to reduce it to physics—the laws of physics seem insufficient to predict the behavior of all chemical reactions. (2) Metaphysical emergence refers to when something is “greater than the sum of its parts” or the irreducible existence of a phenomenon that exists because of an underlying state of affairs. For example, some scientists and philosophers think that the mind is an emergent phenomena that exists because of brain activity, but the mind is not the same thing as brain activity.
reductionism – (1) Relating to identity theories or identity relations. For example, scientists think that water is identical with H2O. (2) The view that something is nothing but than the sum of its parts parts. Some philosophers think that particles and energy (the reality described by physics) is the only real part of the universe and everything else is actually “nothing but” physical reality as described by physicists. Moral reductionists think that moral reality is actually nothing but non-moral facts of some other sort.
instrumental value – The usefulness of something. For example, knives have instrumental value for cutting food.
intrinsic value – Something with value just for existing. We might say happiness is “good for its own sake” to reflect that it is good without merely being useful to help us attain some other goal. If something is intrinsically good, then it is something we should try to promote. For example, if human life is intrinsically good, then all things equal, saving lives would plausibly be (a) rational, (b) a good thing to do, and (c) the right thing to do.
logical possibility – (1) The status of a proposition or series of propositions concerning the rules of formal logic—logically contingent (non-impossible) statements could be true, logically necessary statements have to be true (are tautologies), and logically impossible statements have to be false (because they form a contradiction). For example, it is logically contingent that the Earth exists. (2) A synonym for “logical contingence.” We might say that “it’s logically possible that the Earth exists” rather than that it’s “logically contingent.”
metaphysical possibility – (1) A range of modal categories concerning reality as it exists assuming that the laws of nature could have been different. The range includes metaphysical contingence, possibility (non-impossibility), necessity, and impossibility. Metaphysical possibility can be described as the status of a statement or series of statements considering all possible worlds—A statement is metaphysically contingent if it’s true in some possible worlds and false in others, possible if is true in some possible worlds, metaphysically necessary if it is true in all possible worlds, and metaphysically impossible if it’s false in all possible worlds. For example, some philosophers argue that “water is H2O” is a metaphysically necessary statement. Assuming they are right, if we found a world with something exactly like water (tastes the same, boils at the same temperature, and nourishes the body) but it is made of some other chemical, then it would not really be water. (2) The status of a statement being metaphysically possible (non-impossible) as opposed to a range of modal categories. This status of possibility refers to what could be true or necessarily true about reality assuming that the laws of nature could have been different. A statement is metaphysically possible if it is “true in at least one possible world.” For example, it is metaphysically contingent that the H2O exists because there is at least one possible world where it exists—the one we exist in.
matters of fact – Empirical statements concerning the physical world. They can be known to be true or false from observation. For example, “All dogs are mammals” is a matter of fact. David Hume believed the only statements that could be justified were “matters of fact” and “relations of ideas.”
relations of ideas – Statements that can be justified by (or true in virtue of) understanding the definitions of words. For example, “All bachelors are unmarried” is a relation of idea, and we can justify the fact that it’s true by appealing to the definitions of words. David Hume thought the only statements that could be justified are “relations of ideas” and “matters of fact.”
objective ought – Preferable behavior of a person while considering few (or no) constraints on the person’s knowledge. What we objectively ought to do is often thought to be based on the actual effects our behavior has. For example, utilitarians often say that we ought to do whatever maximizes happiness, even if we have no idea what that is. A person might try to help others by sharing food and accidentally give others food poisoning, and utilitarians might say that the person objectively ought not to have done so, even though the person might have done what was likely to help others from her point of view. “Objective ought” is often contrasted with “subjective ought.”
subjective ought – What we ought to do with consideration of the knowledge of the person who will make a moral decision. What we subjectively ought to do is based on what is reasonable for us to do given our limited understanding of what will happen. For example, some utilitarians say we ought to do whatever we have reason to think will likely maximize happiness. We might say that a person who gives food to a charity is doing what she ought to do as long as it was very likely to help people and very unlikely to harm them, even if many of the people who eat the food have an unexpected allergic reaction. “Subjective ought” is often contrasted with “objective ought.”
reference – (1) The objects that terms refer to. The terms “morning star” and “evening star” have different meanings, but they both have the same reference (Venus). Gottlob Frege contrasted “reference” with “sense.” (2) A source of information used for citations. (3) Someone who can vouch for your qualifications.
sense – (1) What Gottlob Frege called “sinn” to refer to the meaning or description of a word. For example, “the morning star” and “the evening star” both have different senses, but refer to the same thing. Gottlob Frege contrasted “sense” with “reference.” (2) The ability to understand. For example, we might talk about someone’s good sense. (3) To perceive. For example, we might say that we sense people in the room when we can see them. (4) An ability of perception; such as sight, sound, touch, taste, and smell.
Update (6/23/12): I updated the definitions for “logical possibility” and “metaphysical possibility.”