Contingency

What is the case but might not have been - and whether that is a fact about the world or about our ignorance.

Theme: Being and reality
Tradition: Cross-tradition
Term fixed: c. 1020

In plain terms

Most of what exists did not have to. The particular shape of a coastline, the fact that you are reading this, the layout of a keyboard - none of it is impossible to imagine otherwise, and much of it nearly was otherwise.

Contingency is the name for that status. Something is contingent if it is true but could have been false, which puts it between the necessary, which could not have been otherwise, and the impossible, which could not have been at all.

The status turns out to carry an enormous amount of weight. If everything in the world is contingent, then the world as a whole looks like something that could have failed to be - and either that requires explaining, or it is simply how things are and the demand for explanation is a mistake.

As a philosopher would put it

Avicenna's division is between the necessary-in-itself, whose existence follows from its essence, and the possible-in-itself, which requires a cause to exist. Contingent things are necessary through another and possible in themselves, and since a chain of such things cannot be self-sufficient, the series terminates in the necessary existent. This is the argument from contingency, and Aquinas's third way is a version of it.

Leibniz gives it the form still argued over. Nothing happens without a sufficient reason; the contingent facts cannot explain themselves individually or collectively; therefore the explanation lies outside the series in a necessary being. Hume and later Russell reject the demand rather than the reasoning - the universe may simply be there, and requiring a reason for the totality is applying to the whole a demand that only makes sense of parts.

In the twentieth century the notion migrated. Rorty's contingency of language, self and community makes it a claim about the absence of any non-historical vantage point, and the historical sciences - evolution, path dependence in economics - make it a substantive explanatory category rather than a modal one.

Where you meet it

The standard shipping container is 8 feet wide and 8 feet 6 inches high because Malcom McLean, a trucking operator, began in 1956 by lifting the bodies of road trailers onto a converted tanker. The dimensions were the dimensions of American highway trailers, which were set by state road regulations.

ISO 668 fixed those figures internationally in 1968. Every container port, crane, chassis, ship cell guide and rail wagon built since has been dimensioned to them, and the sunk cost is now measured in the trillions. Changing the number is not difficult in the way that difficult problems are difficult; it is simply not going to happen.

So a set of measurements chosen by one American haulier for reasons that ceased to apply within a decade now constrains global trade more tightly than most laws of nature constrain anything. It could have been otherwise and it is now effectively fixed - which is exactly what contingency looks like from inside, and why it is so easily mistaken for necessity.

What is actually disputed

Whether the totality of contingent things needs an explanation.

The argument from contingency holds that it does: individual contingent things are explained by others, the series as a whole is not explained by any member of it, and a sufficient reason must therefore lie outside it. The objection, made by Hume and sharpened by Russell in his 1948 debate with Copleston, is that the totality is not a further thing requiring a cause, and that once every member is explained there is nothing left over to explain.

A second dispute is whether contingency is real or epistemic. On a strong necessitarian view - Spinoza's - nothing is contingent and everything follows from the divine nature; what looks contingent is what we do not see the reason for. The intuition that things could have been otherwise is powerful, and it is not evidence.

Commonly confused with

Chance c. 330 BC Chance is about whether an outcome was determined. Contingency is about whether it could have been otherwise, and a fully determined event can still be contingent because the initial conditions could have differed.

Defined against

Necessity The pair is exhaustive for anything that is true: either it could have been otherwise or it could not

Philosophers

Avicenna The necessary and the possible-in-itself, and the argument built on the pair
Thomas Aquinas The third way, which is that argument in Latin dress
Gottfried Wilhelm Leibniz Sufficient reason, and why there is something rather than nothing
Baruch Spinoza Nothing is contingent; the appearance of it is ignorance
David Hume The demand for a reason for the whole is the error, not the answer

Works

The Book of Healing Where the division is made
Summa Theologiae The five ways, and the third of them
Monadology Sufficient reason applied to the world as a whole
Ethics The denial that anything could have been otherwise
A Treatise of Human Nature The attack on the whole pattern of argument

Schools

Avicennism Where contingency becomes an argument
Thomism Where it is absorbed into natural theology
Spinozism Where it is denied outright
British Empiricism Where the demand for explanation is refused
Classical Pragmatism Where it becomes a claim about vocabularies rather than beings

Related concepts

Necessity c. 330 BC · Possibility c. 330 BC · Existence c. 1020 · Causation c. 330 BC · Chance c. 330 BC

Avicenna's division of beings into the necessary-in-itself and the possible-in-itself, around 1020, is what turns contingency into an argument rather than a description.