I always enjoyed philosophy, but I never thought to ask this question when I was still taking philosophy classes. So, I thought this was a good way to see what "philosophy" people think of this.

When you spend time trying to define terms in philosophy, what are you doing exactly?

Examples: In ethics: what is good? what is right? In aesthetics: what is art? what is beauty? In epistemology: what is knowledge? In social/political philosophy: what is justice?

In these cases, and others I'm sure you can think of easily, what is the goal exactly? To say what the term "should" mean? To say what the term "does" mean, in the sense of how it is used by people? I realize I'm verging on philosophy of language territory here. But I really want to know what people engaged in trying to pin down terms like this think they are doing?

In mathematics, you simply define terms however you want, and the definitions are good or bad depending on what you can do with them, is that the idea? If you just want to know how the terms are used, it seems like that isn't inherently philosophical, more empirical. I would appreciate any perspectives on this!

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    "Classical" philosophy - from Socrates and Plato on, is aiming to "find the essence" of good, beauty, knowledge, etc. This is quite different from what you are describing as the mathematica practice of "defining terms" and ... see what happens. Aug 31, 2016 at 14:26
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    A useful example from the math context can be : compare the math problems regarding number theory with the philosophical problem of "what are" numbers, i.e. the ontology of abstract objects. Aug 31, 2016 at 14:29
  • There are various ways of setting up mathematics. The standard answer to "what is a number" would be "a number is a certain kind of set". If you ask "what is a set", the response is that it is an undefined object subject to a list of axioms (that can vary from system to system). Generally speaking, anything can be called a number if it "does the job of a number", meaning you recover all classical results about numbers.
    – user22973
    Sep 1, 2016 at 14:08
  • What is beuty ? Who is beuty full person for you ? Beuty is internal or external? Jun 9, 2020 at 8:24
  • fwiw, i don't think "what is beueaty" is asking about definitions. i think framing it that way one loses the meaning of the phrase -- which you can just look up in a dictionary
    – user46524
    Jun 9, 2020 at 17:44

5 Answers 5


As a general answer, they are trying to shape the language used in the conversation to help further the conversation along.

I have found the most useful viewpoint on this topic for myself is created by flattening out all of the complexity of defining such words into two directions. One directon occurs when a philosopher seeks acceptance for their theory of what something is by suggesting that a word everyone else has used informally is actually describing the something they are looking at. In such a case, if a philosopher can make an argument that this commonly used informal word is actually the concept they are exploring, they can describe what they are looking at much more succinctly.

The other direction I see for such definitions is to create room for a new category where that category was previously crowded out by others. A trivial example would be if one believed everything was either "good" or "bad," and that it was always clear which was which. A philosopher might try to pin down your definitions of "good" or "bad" enough to suggest that there may be a middle ground between the two extremes where things are a bit murkier. (Likewise, a philosopher engaging in the first direction might seek to take that murky middle region and define "good" and "bad" such that you don't feel there's a need for that middle region at all).

This becomes very important in philosophy because often philosophy deals with extreme scenarios, and controlling the meaning of the words becomes very important. As an example, "do unto others as you would have done unto yourself" gets complicated when one is talking about solipsism, or facing Laplace's daemon. It becomes very hard to interpret such phrases without very exacting meanings for mundane words such as "do."


There's no one answer to this. Plato's use of language was idiosyncratic, and he often used common terms in non-standard ways as a way of reshaping how people conceptualized them. Conversely Wittgenstein believed many classic philosophical problems were reducible to language ambiguities.

The general reason language is important to philosophers is that it is a stand-in for concepts, often ones that are difficult or impossible to communicate directly. As a rough measure, the lucidity of a philosopher's language matches their ability to clearly communicate their concepts.


Definitions aren't the same thing as Demonstrations; and usually they come after.

For example, its easy to demonstrate that numbers are useful; and no-one bothered to define them for two millenia. This doesn't mean that definitions aren't useful - they obviously are; but one must have a clear sense of what purpose they serve.

This is akin to the difference between Knowledge by acquaintance/presence and knowledge by descripton/reference.

I can refer to a tree or describe a table, but this doesn't dispense with actually seeing a tree or using a table - say in setting out dinner for four, and a stranger amongst them.

One has to be acquainted with beauty before beginning to talk about it (aesthetics), and one should be acquainted with the conversations that preceded yours - or at least their high points (so you might aim towards them) or their low points (so as to know what to avoid); similarly with ethics.


Let's be clear about context. Terms like 'good', 'right', 'art' and 'beauty', 'knowledge', 'justice', etc are not created out of whole cloth. They refer to... well, something... that has a distinct and powerful impact on the world. People prefer certain experiences to others; they desire certain things above other things. They want the place they live to be beautiful, clean, and filled with light, not ugly, filthy, and covered in darkness. A leader who has knowledge makes better decisions than a leader who is ignorant; a government that is just satisfies people more than a government that is unjust. The Trojan war was ostensibly fought because of the beauty of one woman; the George Floyd protests are ongoing because Floyd's death triggered a pervasive sense of injustice. We have a pretense in the modern, liberal world that people are rational and thoughtful — a pretense we developed because 17th and 18th century philosophers decided that 'rationality' was a virtue (a 'good') that we should aspire to — but even rationality is motivated and underpinned by value judgements.

If our social and political worlds are driven by concepts like 'good', 'right', 'just', 'rational', and 'beautiful', then it would be useful to have a better understanding of what these terms mean: what concepts or objects they point to. That is what philosophers are trying to suss out.

I know that it's tempting to think of mathematics in purely abstract functional/structural terms, but it's important to remember that mathematics is always used in the service of value. Even something as simple as counting must be evaluated in terms of context: ten dollars is desirable; ten pimples are not. The ancient Greeks saw mathematics in aesthetic terms, from which we get the golden ratio that describe an aesthetic ideal for buildings and other structures, and the harmonic mean which was used to define intervals in musical scales. Even something as metaphorically scientific as 'rocket science' involves value judgements. Why should we do something as expensive, time consuming, and difficult as launching a probe to Saturn? What values does it satisfy that justifies those expenditures?

We cannot avoid the is/ought distinction. If we are trying to decide how to allocate the intellectual and material resources of our selves or our community, we don't generally do it on a coin-flip. So if we're going to be tangled up in 'oughts' as we move forward, we really ought to get a handle on the values and ideals that lie beneath them. So we really ought to try and define these value-specific terms.


You should have clear three facts:

  1. Knowledge serves to survival. Knowledge is essentially divided in facts that are true (a portion of elements that are coherent, for example the fact that reading improves knowledge, and that will finally improve our probabilities of surviving) and things that are not true (elements which are not coherent, for example the fact that knocking your head against the wall increases your probabilities of survival), and therefore decrease our probabilities of survival.

  2. Philosophy seeks for the final truth. You should be aware that science does not, science seeks for empiric truths, therefore, philosophy has a deeper and more wide meaning. Final truths would naturally improve our probabilities of survival, as a group, and in the long term. Truths are essentially propositions, relationships between subjects and objects (e.g. Drinking water(the object) is(relationship) good (for us, the subject). Relationships between concepts depend, obviously, on the existence of useful concepts.

  3. Concepts are atomic elements of knowledge that are the foundations of truth. Concepts are usually written in a dictionary, but reading a dictionary is not enough to gather the meaning of concepts. I always repeat that a dictionary is a set of self-contained references, therefore a set of tautologies. In order to understand a concept, you need to have lived in this planet, and experienced more or less what the rest of us have experienced. If I tell you that the sky is blue, you need to understand what is the sky, and therefore, what is not the sky; if the sky is "a region of the atmosphere", you need to know what is a region and therefore what is not a region, what is the atmosphere, and so on. So, in order to understand an apparently simple proposition made by the relationship between two concepts ([SKY]<-(to be)->[BLUE]), you need a lifetime of experience.

Synthesizing, we experience life, and with such experience we came to define concepts, which will help us to form the body of our knowledge, which will help us surviving. That's why we need to know things like "what is justice?", because that help us getting facts of knowledge, that will ultimately increase our probabilities of survival.

It is important to remark that the truth (even if it is final) is subjective. If I'm an elephant, jumping to the sea might decrease my probabilities of survival. But not if I'm a fish. If I'm a killer, surviving is my largest priority. If I'm a member of the society victim of such killer, the death of the killer increases my probabilities of survival. A final truth would only be same for all if all of us would be absolutely identical and no subjective bias would exist.

Disclaimer: no references, despite the ideas here are just logical conclusions. They are part of the book I'm currently writing.

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