Philosophy is as much a language as anything else. Learn the terms here so that you can both follow what is being said and communicate precisely what you want to, to others.

• Teleology - Things are guided by their purpose
• Epistemology - How the Fuck do you know anything?
• Metaphysics - What the Fuck is the World?
• Ontology - The Fuck itself

Why bother with the jargon?

Philosophical terms are not decoration. Each one is a label on a whole family of questions, so that two people can agree on which question they are arguing about before they start arguing. Most pointless debates are two people answering different questions with the same words. Learn the labels and half the confusion goes away.

The big four, in plain words

Metaphysics: what is there, really?

Metaphysics asks about the basic nature of reality: Is the world made of matter, mind, or both? Is time real or an illusion? Do we have free will? The name is an accident: Aristotle’s editors put his book on “first philosophy” after (meta) his Physics, and the title stuck.

Ontology: what kinds of things exist?

Ontology is the inventory department of metaphysics. Do numbers exist? Do holes? Do nations, or just people? A useful test from the philosopher W. V. O. Quine: you are committed to whatever your best theory needs to quantify over, whatever it says “there is”. If your physics says “there is an electron”, you owe electrons a place in your ontology.

Epistemology: how do you know?

Epistemology is the theory of knowledge. The classic definition is that knowledge is justified true belief. In 1963 Edmund Gettier wrote a three-page paper showing cases where you have a justified true belief by luck (a stopped clock that happens to show the right time) and yet don’t seem to know. Philosophers have been patching that definition ever since.

Teleology: what is it for?

Explaining by purpose or goal. See the Teleology page.

A few more that come up constantly

• Ethics – what we ought to do, and why. Its main families are consequentialism (judge by outcomes, as in Jeremy Bentham’s utilitarianism), deontology (judge by duties and rules, as in Kant) and virtue ethics (judge by character, as in Aristotle).
• Aesthetics – beauty, art and taste.
• Logic – what follows from what. See Logic.
• Phenomenology – the study of experience as it is lived from the inside.
• Empiricism vs Rationalism – does knowledge come mainly from the senses (Locke, Hume) or from reason (Descartes, Leibniz)?
• A priori vs a posteriori – knowable before experience ($2 + 2 = 4$) or only through it (water boils at 100°C at sea level).
• Materialism / Physicalism – everything that exists is physical.
• Idealism – reality is fundamentally mental.
• Dualism – mind and matter are two different kinds of thing.

How to use a term well

Three habits help more than memorising definitions:

1. Ask which question a word belongs to. “Is that true?” can be logic (does it follow?), epistemology (how would we know?) or metaphysics (is there a fact of the matter?).
2. Watch for one word doing two jobs. “Natural” can mean found in nature, normal, or morally fine. Arguments that slide between those meanings are cheating, usually without knowing it.
3. Look for the opposite. A term is clearest next to its rival: realism versus anti-realism, determinism versus free will, a priori versus a posteriori.

An everyday analogy: the detective

A detective at a crime scene does all of philosophy at once. What is in this room? (ontology). What really happened? (metaphysics). How can I be sure, and is that footprint real evidence? (epistemology). Why did the culprit do it, what were they after? (teleology). Was it wrong? (ethics). Does the conclusion follow? (logic).

A worked example: “Is the colour red real?”

Watch the terms split one vague question into several sharp ones:

1. Ontological: Does redness exist as a property of the apple, or only as light of roughly 620 to 750 nanometres reflecting off it?
2. Epistemological: How do I know your red looks like my red? (This is the “inverted spectrum” puzzle.)
3. Metaphysical: If redness is an experience, is experience itself physical? This is the “hard problem of consciousness”, named by David Chalmers in 1995.

Same three words, three different debates, each with a different kind of answer.

Common misconceptions

• “Philosophy is just opinion.” It is argument. Positions are judged by whether their reasons hold up, the same way any proof is.
• “These terms are fixed.” They shift between traditions and centuries. Always ask how an author is using a word.
• “Science has replaced philosophy.” Science answers many questions philosophy once asked, and philosophy keeps clarifying what science’s answers mean. See Philosophy in Physics.

How it connects

• Philosophy and Philosophers to Study
• Abstraction, Number Theory and Set Theory for ontology in mathematics.

The truth revealed: learn the words, and you find out what you were actually arguing about.