It makes sense to me that when proposing an analysis of a property we should be certain about what that analysis is. To achieve this certainty I think that necessity would be the ideal way to determine what those properties are. But it seems that some examples of analyses don't always involve necessity, does anyone know why necessity isn't always involved in an analysis?

Here are two examples of analysis. The first analysis (example 1) of the property of "being green" proposes the property of "being coloured" as a constituant of the property of "being green". The second analysis (example 2) of the property of "being a sibling" proposes the properties of "being a brother" and "being a sister" as being constitutants.

Example 1

 "To be green is to be coloured".

Example 2

"To be a sibling is to be either a brother or a sister".

In Example 1 the property of "being coloured" relates to the property of "being green" by necessity since anything that instantiates "being green" automatically instantiates "being coloured". However in Example 2 the relation of necessity doesn't seem to be between the property of "being a sibling" and "being a brother", and it also does not hold between the property of "being a sibling" and "being a sister".

So it looks like the necessity is not always present in analysis. Does anyone know why necessity isn't always involved in analysis? If anyone could shed some light on this problem i'd be very grateful. Thanks.

  • I don't see the difference? if I have a brother I have a sibling; if something is green it has a colour. and can you not just write the 2nd example just as much into "to be a brother or a sister is to be a sibling". both involve necessity but in the 2nd there is also a sufficient relation (unless we're non binary). maybe I'm not getting the question.
    – user62233
    Commented Aug 18, 2022 at 14:54
  • if you're asking why isn't every if an iff then I guess it's like asking why isn't every 4 sided shape a square. just means different things
    – user62233
    Commented Aug 18, 2022 at 15:01
  • Necessity does not distribute over disjunction. "Being a sibling" is necessarily "being a brother or being a sister", but, by the meaning of disjunction, necessity cannot possibly attach to either disjunct separately.
    – Conifold
    Commented Aug 18, 2022 at 23:12
  • This said, necessity is, at best, an unreachable ideal, and most existing conceptual analyses are just rough approximations of what they analyze with no necessity attached, see SEP, Concepts:"There are too few examples of successful definitional analyses, and certainly none that are uncontroversial". Most interesting concepts are simply not analyzable into something else. The example of knowledge (analyzed into justified true belief or variations) is typical, over 2000+ years all attempts at exhaustive analysis failed.
    – Conifold
    Commented Aug 18, 2022 at 23:24
  • If conceptual analysis depends on necessity and your question belong to the upper ontology of conceptual analysis category, then you must necessarily find its answer one day… Commented Jan 16, 2023 at 7:18

2 Answers 2


Conceptual analysis certainly DOES require necessity. No analysis of units of meaning would ever ignore the impossible, the probable and improbable, the possible, and the certain.

There are several types of necessity according to traditions in philosophy, but the concepts of necessity and contingency are rooted in deeper metaphysical questions, such as what is metaphysical necessity itself? Let's take a look at some of the types of necessity that philosophical analysis relies on broadly.

Logical Necessity

In logical necessity, the emphasis is on the logical operators. In your second example, for instance, you have used exclusive disjunction. It is necessary a sibling is either a brother or a sister but not both. Setting aside the intensions of the words, one might ask if the logical relation you present is accurate. Is your claim true in the face of the possibility a sibling might be born and determined to be intersex? Here, the consequence being examined is the disjunction itself.

Nomic/Nomonological Necessity

According to the SEP's Varieties of Modality, some philosophers hold certain necessities are guaranteed by causal determinism, empirical fact, or laws of the universe, which are necessarily weaker or stronger than metaphysical necessity, depending on the philsoopher. From the article:

We are inclined to say that nothing can move faster than light to express the fact that the laws rule out superluminal motion, and to state Newton’s First Law by saying that an object cannot depart from uniform rectilinear motion unless acted on by an external force. This motivates the thought that there is a form of necessity associated with the natural laws.

Causal Necessity

Also known as (causal) determinism, this is the view that events in time are essentially necessary given prior events. This is classic territory in regards to the nature of the physical universe, Newtonian mechanics, and questions of free-will

Metaphysical Necessity

Given my limited expertise, this is the most contentious of necessities which seems to cover various philosophers views on a bewildering array of claims regarding the analytic-synthetic divide, a prioriticity and a posteriority, universals and particulars, entities and properties, modality and necessity itself, and so on. Here, the giants of philosophy use the term when squaring off about first principles. Here, philosophers seem to invoke broad claims of necessity about philosophical positions or what SEP calls metaphysical grounding. From the article:

Some suggest that this and similar claims are grounding claims, where grounding is understood to be a form of constitutive (as opposed to causal or probabilistic) determination or explanation. The point of departure for theorizing about grounding is that there are a variety of claims—claims we make in ordinary life as well as ones we make in the context of doing philosophy—that are best interpreted as being claims about what grounds what. As for metaphysics in particular, some claim that grounding plays a central role in the enterprise properly conceived. Schaffer, for example, writes that “metaphysics as I understand it is about what grounds what” rather than what exists (2009: 379)

When debating existence, for instance, one often appeals to grounds to prove existence.

Linguistic or Semantic Necessity

This is the one you ask after. In linguistics, the relationship between green and colored is one of hyponomy/hyperonomy. That is, it is necessary that green things are colored, but note that it is not necessary that colored things are green. This is a form semantic necessity because it is derived from the relationship of the intensions of words.

Why Your Second Example Includes Necessity

When you say:

To be green is to be coloured.

You can paraphrase as 'If something is green, then it is coloured' (G->C). When you say:

To be a sibling is to be either a brother or a sister.

Necessity also exists. By paraphrase, 'If one has a sibling, it is either a brother or a sister' (Sib->Bro XOR Sis). In both cases, you are dealing with the conditional, and it is this conditional logical expression that encapsulates necessity. It just so happens that you have exclusive disjunction in the consequent of the second one. The presence of conjunction and disjunction in conditional claims doesn't undo the necessity built into the claim as a whole. Thus, if one has a sibling, it is necessary that one has a sibling (Sib->Sib), and most accurately if one has a sibling, it is necessary that is a brother, sister or an intersex sibling (Sib->Bro XOR Sis XOR Inter) at least in real world cases.


There is necessity in both examples in the question.

If green then necessarily color(ed)

If sibling then necessarily bro/sis

The two possibilities (bro/sis) threw you off it seems. Necessity can range over possibilities. It's necessarily possible that there's liquid water here means it's established beyond doubt that it's possible that there's liquid water here. May be you found out the temperature here is 25 degrees celsius.

The converse is true as well e.g. this bottle water is possibly necessary. which means it is possible that the water bottle will become necessary e.g. if you lose all the other water bottles.

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