What Is a Necessary Being? Something That Could Not Have Failed to Exist

A contingent thing exists and might not have, so its non-existence is coherent and describing a world without it involves no contradiction. A necessary thing, if there is one, exists in every possible way things could have been, so its non-existence is not merely improbable but impossible. The distinction is about modality rather than about duration, since something could last forever without being necessary, and something necessary is not necessary because it is old. Numbers and mathematical objects are the usual candidates outside theology, on the view that it makes no sense to describe a world where two and two fail to make four. The question of whether any concrete thing, meaning anything in space and time or anything causally efficacious, could be necessary is where the disputes concentrate.

The concept does work in several arguments and the work is the reason it is defended:

• •It terminates a regress, since a chain of things each explained by another needs something that does not require the same explanation
• •It answers the question of why anything exists rather than nothing, if the answer is that something had to
• •It supports cosmological arguments, which move from contingent things to a necessary ground for them
• •It gives a foundation that is not arbitrary, since a necessary thing is not a brute fact that happens to obtain
• •It grounds necessary truths on some accounts, if those require something to make them true
• •It supplies the traditional conception of a deity as existing by nature rather than by circumstance

Several serious challenges have been pressed and none is universally accepted as decisive. The strongest holds that existence is not a property a thing can have necessarily, and that all necessity is a feature of propositions and of how concepts relate rather than of things in the world, so the notion of a necessarily existing object is a confusion. A second argues that if something can be conceived not to exist then it does not exist necessarily, and that a concrete thing can always be so conceived. A third points out that the arguments requiring a necessary being generally rely on the principle that everything has an explanation, and that principle is itself contested. A fourth accepts brute contingency, holding that the universe simply exists with no further explanation, which is unsatisfying rather than refuted.

The word covers several distinct notions and separating them prevents a good deal of confusion. Logical necessity means the denial involves a contradiction. Metaphysical necessity is broader, covering things held to be necessary in the nature of the case without being contradictions to deny, and the standard examples concern the essential properties of substances. Physical necessity means required by the laws of nature, which are themselves contingent on most accounts, since the laws might have been otherwise. Analytic necessity follows from the meanings of words. Conceptual necessity follows from how concepts relate. An argument moving between these without noticing is a common failure, since establishing that something is necessary in one sense establishes nothing about the others, and several disputes about necessary existence turn out to be disputes about which sense is meant.

One argument tries to derive existence from the concept alone, holding that a being than which nothing greater can be conceived must exist, since a being existing only in the understanding would be less than one existing in reality. The argument has been restated in modal terms, holding that if a necessary being is possible then it exists, since something possible in every possible way things could be is actual. Objections are old and numerous, with the classic reply that a perfect island could be conjured by the same reasoning, and the standard modern objection that existence is not a perfection or a predicate of the relevant kind. The modal version shifts the difficulty onto whether such a being is genuinely possible, which cannot be established by finding no contradiction. The argument is rejected by most philosophers and has never quite been finished off, which is itself interesting.

A necessary thing exists in every possible way things could have been, which is a claim about modality rather than duration, and numbers are the usual candidates outside theology. The concept terminates a regress and answers why anything exists, if the answer is that something had to. Objections hold that necessity belongs to propositions rather than things, and the principle that everything has an explanation is itself contested.