My specific question that I want answered is: Among definitions, how do we choose which one is the best?

When it comes to definitions of abstract concepts, it seems like we can define things willy-nilly. I say, "willy-nilly" because there's no concrete thing to which to compare our definitions. For example, some define marriage as between a man and woman, but others say it's simply between two people who love each other. But the fact remains that there is no such thing as marriage-ness against which we can test our definitions. I can't run and go get some marriage and say, "See! Look, I'm right!"

So what basis do I have to say my definition is true? What process do philosophers use to tackle an issue like this? When it comes to questions like "What is marriage?" or "What is justice?", what's a good starting point to come to some sort of conclusion? I ask because it seems like how we define these things is left to our own arbitrary whim.

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    I'm having a bit of trouble parsing out what from several possibly legitimate SE-answerable questions you want to ask. Do you want to (1) understand the process of picking "best definitions" i.e., a question of practical wisdom, (2) ask what might guide philosophers in defining the nature of a social institution like marriage? (3) take a position in the debate about "universals" / "Forms" / "concepts"?
    – virmaior
    Commented Jun 22, 2016 at 13:08
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    Definitions and concepts are different things. The first are usually hypothetical or speculative, and do not have to be "verified", except for their internal consistency and relevance. Commented Jun 22, 2016 at 14:45
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    A def can't be true or false. It's just a predicate that some things satisfy and others don't. It's a "classifier." If we say an even integer is an integer divisible by 2, that's not right or wrong. It's just a predicate we apply to integers. 5? Not even. 6? Even. If we'd called numbers divisible by 2 "prime," then 6 would be prime. A definition is just a predicate.
    – user4894
    Commented Jun 22, 2016 at 16:41
  • To virmaior: Answering (1) answers (2). If we're going to define the nature of a social institution, then we need to know the process of picking best definitions. That happens to be what I want to know. Commented Jun 22, 2016 at 18:12
  • If you add deontological value to a definition, then it ceases to be just that. Commented Jun 22, 2016 at 18:29

4 Answers 4


Definitions are established by agreement or convention, so the main consideration in using definitions is to try to maintain them in accordance with established usage. It should also be kept in mind that since they are arbitrarily established, they are "vacuous", as Quine says. That means that they don't communicate any propositional truth except to assert that some convention exists for the defined usage. As Quine says:

"In each case the statement inferred through the definition is true only because it is shorthand for another statement which was true independently of the defnition. Considered in isolation from all doctrine, including logic, a definition is incapable of grounding the most trivial statement;" (Quine, "Truth by Convention")

Although assigning a term to some concept is arbitrarily established by convention, the truth of what is predicated of that concept must be determined by some independent means. In terms of predicate logic, definitions are often expressed using the biconditional:

∀x[Dx ↔ Px]

That means that x being defined as D implies that it can also be predicated as P. The reverse is also true: If x can be predicated as P, then it is defined as D.

However, as stated before, such a definition asserts nothing except for an agreed convention of usage. It does not assert that there exists anything that conforms to the definition. In terms of predicate logic, that means that the predicate Da, asserting that "a is D", would have to depend on something other than the definition for its truth value.

That also means that any additional assertions about Da would have to be established in accordance with the definition. For example:

1. ∀x[Dx ↔ Px]
2. Da & Na
3. Pa & Na

Line 2 says that some new predicate N can be asserted of something defined as D. Line 3 follows from 1 and 2. Thus, being Na must be consistent with Pa. The definition in line 1 doesn't establish the truth of either line 2 or 3; but lines 2 and 3 must be consistent with the definition since it was defined as such.

New Definitions

When it comes to creating new definitions, we should keep in mind the purposes for which they exist. Our use of language and logic involves our efforts to understand how reality behaves. We proceed with the assumption that there is a certain regularity to that behavior and that things operate according to fixed principles. Thus, we classify objects according to their properties, and those properties are related to principles that describe their behavior. Therefore, the creation of new definitions should not lose sight of the principles that give rise to our interest in forming them. They should reflect those properties which we believe enable a given object to be subsumed under a principle of interest.

Application to Plato's Republic

As pointed out in a comment, the definition of justice was discussed at length in Plato's Republic. For Socrates and the other participants of the discussion, the designation of the word δικαιοσύνη (justice) to the concept had already been long established, so the arbitrary assignment of the "shorthand", as Quine called it, was far from being the topic of discussion. Rather, the concept of justice is something that we all have a certain sense of, so it's not difficult to know what is being referred to when we speak of it. The difficulty and the object of discussion in the Republic was knowing the extent of what could be predicated of justice. In terms of my proposition above, it was not the arbitrary question of assigning Dx to Px; but rather, it concerned the nature of the concept itself as represented by the formula Px. As I said before, that is not arbitrary and must be established by some independent means.

For Plato, the concept of justice referred to a plurality of objective forms. This can be seen in the following passage in which the words justice and injustice are both in the plural:

"Well then, that soul is immortal both the recent argument and the others would compel us to accept. But it must be seen such as it is in truth, not maimed by community with body and other evils, as we now see it. But what it is like when it has become pure must be examined sufficiently by calculation. And one will find it far fairer and discern justice (δικαιοσύνας) and injustice (ἀδικίας) and everything we have now gone through more distinctly. Now we were telling the truth about it as it looks at present. However that is based only on the condition in which we saw it." (The Republic, Book X, 611c)

Given that Plato believed that justice is objectively real, it was not something that could be established by mere convention. Rather, its nature had to be discovered, and we find that he believed that the difficulty with this was due to its being mixed up in the "community" (κοινωνία) of the body and other evils.

The question at hand is how we establish definitions of this sort in which an arbitrary designation Dx must be assigned to some objective determination Px. Given that our understanding of Px may be subject to further discovery and change, it's best to try to incorporate the determining factor into the definition rather than to try to describe a changeable list of what is determined by it. Plato believed that determining factor would be the universal forms, but I, of course, believe that it is God who determines what it just. Therefore, a proper definition would reflect the fact that the extent of justice is defined by God's moral standard.

  • If definitions are arbitrary, though, then what's the point in arguing over them. We have no philosophical basis to say, "Justice should be defined this way," in which case The Republic was a waste of time. What methods do philosophers employ to come to definitions that are good and true? Commented Jun 22, 2016 at 18:09
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    You're speaking of something that isn't purely a definition. The idea the justice should be defined in a certain way assumes some objective standard to be discovered rather than to defined. If there were no such standard, why should it be anything but completely arbitrary?
    – user3017
    Commented Jun 22, 2016 at 18:59
  • As I said in my answer, definitions should not lose sight of the principles to which they are intended to reflect. It is not man, but God who determines what is just, so whatever definition we use must reflect the fact that the boundaries are not determined by our definition but by God. For example, we might say that justice is conformity to God's moral standard of equity.
    – user3017
    Commented Jun 22, 2016 at 20:07
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    @SpencerJacobs The purpose of arguing over definitions is that much content is written using those definitions with the assumption that the reader is using a definition sufficiently consistent with the writer's definitions. If one writes a bunch of content about marriage (such as a set of laws for a nation), successfully redefining marriage arguably changes the semantic meaning of all of that content written using that word. In many cases, it may not be affordable to even go back and properly annotate all previous writings to account for the new definition.
    – Cort Ammon
    Commented Jun 23, 2016 at 1:13
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    Or, putting it more succinctly, the ability to control definitions is the ability to control the ultimate power of the pen. One who controls definitions can easily overwhelm the power of the sword.
    – Cort Ammon
    Commented Jun 23, 2016 at 1:14

Looking at philosophy as the wrapper around science, with a similar process of evolution we can look at this from a "late-Wittgenstein" point of view. From that point of view, all communication takes place within some 'language-game' which embodies a "Kuhnian" paradigm -- an interconnected set of models that are used to incorporate information, while being continually tuned to cover more and more of the incoming information over time.

Definitions are just elements of a paradigm, and so we seek the same traits in them that we seek in theories overall:

  1. Stable reference -- we want the definition to be well-defined, so that the things to which it refers do not change without actual changes in the attributes relevant to the problem domain. In the simplest case, when we define something mathematically, we need to prove the definition fits the axioms of an equivalence relation. For less exact domains, we expect appropriately relaxed standards, but with comparable effects.

  2. Intuitive model -- we want it to be reasonably easy to invoke the appropriate model in the imagination of others either by analogy or through construction of some kind, at least if they have a good picture the other rules of the domain. The whole paradigm itself needs to be capturable by a wide range of people, and particular definitions should not impede that to no end.

  3. Parsimony -- this is dual:

    a. we want the definition to be concisely statable in terms of the other definitions in the same paradigm and

    b. we do not want definitions that push "Occams' razor" aside, and create unnecessary possibilities for expansion of the topic without any basis beyond the implications of the definition itself.

  4. Testability -- we want the definition to apply to the cases toward which it is aimed, and ultimately for the applicability of the definition to be testable or provable in some way.

But when it comes down to society-shaping definitions like that of marriage, the problem is that we approach the same question from incommensurable paradigms. There is no way to argue about the definition in isolation, one must grasp the two worldviews in which the two definitions are embedded and choose one over the other, or derive something in between.

Those who want a narrow definition may see marriage as something we actively support as a culture, and would like the resources and attention to go where they strengthen the culture itself. Those who want a very broad one may be concerned about the costs of stigmatization that happen when family structures do not efficiently fit into the overall pattern of the society.

The former paradigm is that "we have a culture". The later is that we are a pluralistic multiculture, and "we have no single culture". Arguing out the compromise between those paradigms cannot be done by focussing on their effects on a single word. So this, like many arguments centered on words, is ultimately not about definitions at all, it is about paradigms.

It does not matter how you define marriage, it matters how that definition relates to your notions of justice, culture, efficiency, freedom, support, etc. So the right way to set about deciding upon a definition is to realize what it will be embedded in, and to decide what role you expect it to play in a broader philosophical system.


I like to use specific examples to try to convey my thoughts clearly. So, using "marriage" as an example, I find it has at least 4 "best" definitions: 1)personal, 2)group, 3)culture, and 4)legal. Obviously, which one is best, depends on who is doing the definition.

I have my own definition of marriage, and I ignore the other definitions, except the legal definition (because I have to conform to it).

A group of people might get together and agree on a definition that is acceptable to all in the group.

The culture of an area might dictate the definition for most of the individuals living in the given culture.

But ultimately, the legal definition, will be the one that prevails (until it is legally changed).


yes but if we take true that nature has regularity to define something then why we say that we need falsifability in science ?if we define something with its properties these properties shouldnt change..but if they dont change why have paradoxes like raven paradox ? imagine a cup of coffee..we all know how coffee smells..but what if tommorow smells different ? then it will be no coffee? all definitions are given in my opinion through the laws of physics and science general..sciences (physical) tell us about the world but to communicate with him we define objects etc...imagine a gun when instead of the bullet go down because gravity it will go up ? is it still a gun? so we must keep in mind that nature dont want to trick us..

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