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.