The Great Conversation:
Necessity & Contingency

By Gabriel Blanchard

Though the pair may sound abstract, the ideas of necessity and contingency are interwoven with a vast range of topics.

The meanings of necessity and contingency are closely paralleled by the meanings of must and may. Take the premises “Socrates is a man” and “all men are mortal”: if both are true, then Socrates must be mortal (necessarily). But if we exchange the second premise for “some men have brown hair,” then the only conclusion we can draw is that Socrates may have brown hair; it is also possible that Socrates has some other color of hair, or none at all. These sorts of things, things which are possible but not necessary, are contingent (as when we speak of planning for contingencies).

Within this relatively simple framework, we can distinguish multiple kinds or levels of both necessity and contingency. If Socrates is the brother of Diotima, it is necessarily true that Diotima is the sister of Socrates—but that initial if is doing a lot of work. Socrates might have no sisters, or he might have sisters but Diotima not be one of them; their sibling-hood is necessarily mutual if it exists at all, but its existence as such is contingent. The necessity involved is a kind of secondary or conditional necessity: you could even call it both contingent and necessary, depending on the context.

The necessity-contingency pair is often associated with questions of ontology, or the study of being. One of the principal questions of philosophy is whether anything is absolutely necessary—whether there is any entity, or force, or substance, or what have you, that must exist, such that positing its non-existence is simply a contradiction in terms, like positing a dark light. Most philosophers in our tradition, especially (though not by any means only) the religious philosophers, have answered yes to this question; from St. Augustine to Alfred North Whitehead, many of them have specified that this “necessary being” is one of the things that is meant by the word God.

St. Thomas Aquinas goes further than this, making the idea of contingent being one of his five proofs for the existence of God. The argument runs like this: all the things we see around us are contingent; they do not have to exist, they did not always exist, and and they will not last forever. But if everything were contingent, then, with infinite time, we should long ago have reached the point where every contingent thing had lapsed into nothingness. (Though its scope is more limited, covering only matter and energy, the second law of thermodynamics forms an analogy to this argument.) Therefore, all contingent things must be sustained by some necessary thing: even if some contingent things depend on each other, that just knocks the problem one step further back, so to speak, since those other contingent things have to rely on something too. Hence, in order to avoid a “turtles all the way down” scenario, we must posit the existence of a necessary being; and we may call this being God.

"Contrariwise," continued Tweedldee, "if it was so, it might be; and if it were so, it would be; but as it isn't, it ain't. That's logic."

Lewis Carroll, Through the Looking-Glass

These ideas impinge on other arenas as well, such as free will. It seems intuitively true that, when we decide to do something, we could have decided otherwise; our decisions are contingent. Is that the same thing as free will? Especially when we bring in questions like circumstance, available options, bias, addiction, and so forth? If we accept a determinist view of the world, is that the same thing as all actions being necessary? Presumably not: if the characters in a novel were conscious, everything they experienced would be deterministic due to the “omnipotence” of the author, but insofar as the author decided how to write the book, these things would still be contingent. The doctrine of providence—itself a major sticking point between certain Christian schools of thought—hinges precisely on this issue. In his Consolation of Philosophy, Boëthius discusses the problem of how divine foreknowledge can coexist with human liberty, since part of the Christian doctrine of God is that his knowledge is perfect, and if he knows that we are going to do something, how are we free to do otherwise? Boëthius’ own answer was that God, being beyond time, does not so much “foresee” our actions as simply sees them in a boundless present, the present being the sole moment of time in which freedom is truly experienced, which no more invalidates our free will than our remembering the past works backward to remove our past freedom.

Necessity and contingency are thus seen to be related to ideas like causality and chance, in that not only esoteric fields like ontology, but hard sciences like physics and social disciplines like psychology, have to deal with them. Several authors of the Enlightenment, including Thomas Hobbes and David Hume, argued that in the problem of free will, interior “compulsion” was fully compatible with liberty, and only external forces (like threats or bribes) genuinely interfered with human freedom. But very few modern psychologists who deal with addiction would agree; the normal human process of simply “deciding not to do something” is not merely difficult for an addict: it is so hard, it has become a different kind of problem for them.

In many forms of moral theology, particularly Catholic moral theology, this issue of necessity or compulsion versus contingency or liberty is a crucial element in determining responsibility. It does seem intuitive that a wrong act committed under duress, or even due to certain internal factors like ignorance or immaturity, is less reprehensible than an intelligent and premeditated one. This suggests that morality lies entirely in the realm of the contingent: acts deserve blame or praise precisely insofar as the agent could have done otherwise.

This in turn prompts the question of whether “necessary evils” exist. If a thing is necessary, is calling it evil a coherent use of language? If something is evil, does that prove that it is contingent? Utilitarianism, since it considers maximizing human happiness the highest good, has traditionally been willing to countenance things that almost everyone would call evil if only they serve to promote happiness; but, granted utilitarian premises, it is perhaps the general verdict of those things as evil that is at fault. The Christian tradition has mostly answered the above questions “No” and “Yes” respectively, but with some exceptions—St. Augustine argued that legal prostitution was a necessary evil, and even the Exsultet, the traditional Catholic hymn of the Easter Vigil, includes a notorious couplet about the fall of man: O surely necessary sin of Adam, which by the death of Christ was destroyed; O happy fault, which merited to have so great and glorious a Redeemer.

Suggested reading:
Æschylus, Prometheus Bound
Aristotle, On Interpretation
St. Anselm, Why God Became Man
Dante Alighieri, Purgatorio
Baruch Spinoza, Ethics
Sigmund Freud, General Introduction to Psychoanalysis

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