Why is there something rather than nothing?
Everything we know of might not have existed — that is what makes it the kind of thing that needs explaining. A universe that could have failed to be here does not account for itself just by being here. Either the chain of explanations ends in something that could not have failed to exist, or it ends in a shrug.
Leibniz thought this was the first question anybody should ask, and it is not the same question as “what caused the Big Bang.”
You could grant that the universe has always existed and this question would still be standing. It is not about how things started. It is about why there is anything at all to have started.
Two ways of existing
The argument turns on a distinction that sounds technical and is not.
Some things could have failed to exist. This laptop. The Alps. You. Nothing about any of them made them inevitable — change the past a little and they are simply absent. Philosophers call these contingent.
Something would be necessary if it could not have failed to exist — if there is no possible arrangement of reality in which it is missing. The number seven is the usual example: there is no world where seven is not there.
Now ask which one the universe is. Is there something about it that made it unavoidable? It does not look that way. Physicists routinely describe universes with other laws and other constants, and none of those descriptions contains a contradiction. This one seems to be an option that happened to be taken.
Why that matters
If a thing could have failed to exist, then its existing is a fact that stands in need of some account. Not necessarily a cause in time — just an explanation.
We apply this everywhere without thinking. Tyre tracks in the mud, a watch in a field, four faces carved into a mountain: in none of those cases do we say it is simply there. We assume there is a reason, and we go looking for it.
The contingency argument asks you to keep doing that one step further out. The universe is the largest contingent thing we know of. Applying the same instinct gives you three options and no more:
- It explains itself — but contingent things by definition do not.
- It is explained by something else contingent, which then needs its own explanation, and so on with nothing ever settled.
- It is explained by something that exists necessarily.
Only the third one terminates.
What that something would have to be like
Follow the properties, as with any of these arguments, and see what you get.
It cannot be contingent, so it is not the kind of thing that might not have been. It cannot be part of the universe, since it explains the universe. Which means not made of matter, not located in space, not inside time.
That is a long way short of Christianity. It is also a long way past “nothing”.
The honest reply, and what it costs
The serious atheist answer is to deny the first move: perhaps the universe is a brute fact. It exists, there is no reason, and the demand for one is a habit we have picked up from dealing with small things inside the universe.
That is coherent. It cannot be refuted. But it is worth noticing what it does: it makes an exception, at exactly the point where an explanation would be inconvenient, to a principle we rely on everywhere else. It says the tyre tracks need an account and the road does not.
You are then in this position. Either something exists necessarily, or the whole of reality rests on a fact with nothing under it. Both are strange. The question is which strangeness you find more believable — and that is a real question, not a trick.
Objections answered
Why can't the universe itself be the necessary thing?
It might be, and Hume asked exactly that. The difficulty is that the universe does not behave like something that had to exist: it is made of parts that could have been arranged otherwise, running on constants that could have had other values, and on current evidence it began. Necessary things are not usually found to have started.
Physicists say the universe came from nothing.
Read what they mean by nothing. It is generally a quantum vacuum — a state with laws, fields and energy, which is a very unusual sort of nothing. That is a claim about how something became something else. Leibniz’s question is about why there was ever anything for the laws to describe.
Isn't 'God exists necessarily' just an assertion?
It is a proposal, and the argument earns it rather than assuming it: the regress has to stop somewhere, and it can only stop at something non-contingent. What Christians then add — that this necessary being is personal — comes from elsewhere, and it is honest to say so.
Shared ground, and where traditions differ
All Christians hold
All the traditions hold that God alone exists in and of himself, and that everything else is held in being by him moment to moment — a claim they take from Scripture rather than from Leibniz, who arrived at it much later and by another road.
Roman Catholic
Has the most developed version of this in Aquinas, whose third way argues from the contingent to the necessary and is the ancestor of Leibniz’s formulation.
Related questions
Inspired by Reasonable Theology — "Why Is There Something Rather Than Nothing? Leibniz's Contingency Argument". The argument is theirs; the words here are ours.
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