Evidence · Case 09 · Atheism
Gottfried Leibniz and the argument from contingency
One exhibit from the free evidence repository at apologetics.pro.
One common form of the argument. Whatever exists has an explanation, either in the necessity of its own nature or in an external cause. The universe exists. A collection of contingent things cannot be its own explanation. Therefore there is a necessary being that explains it. The argument turns on the difference between things that could have been otherwise and something that could not fail to exist.
Sources
Objections & responses
- The argument commits the fallacy of composition. Each part of the universe may be contingent without the whole being contingent, and each part may be explained by earlier parts in an infinite regress that needs no further explanation.
This is Hume’s objection. The reply is that explaining each member of a series by the previous member does not explain why the series exists at all, or why it is this series rather than another; a chain of borrowed existence still needs something that does not borrow. Defenders of the argument also note that the composition fallacy does not apply automatically: if every part of a wall is brick, the wall is brick. Whether contingency composes in that way is a fair question, and Hume’s regress reply deserves to be weighed alongside the response.
- The principle of sufficient reason leads to modal collapse: if God’s choice to create this world has an explanation, he couldn’t have chosen otherwise, so everything is necessary. Doesn’t van Inwagen’s argument show the principle undermines itself?
Van Inwagen’s objection is a serious one. The standard reply, from Alexander Pruss and Joshua Rasmussen, is to weaken the principle: not everything needs an explanation, but every contingent fact does, and a free choice can be explained by the agent’s reasons without being necessitated by them. Whether a restricted principle avoids collapse while still supporting the argument is exactly the technical debate. The argument’s strength depends on how much weight the principle can carry, and that is the honest summary of where it stands.