And in this case, "life begets life" is clearly a presupposition to the theory of evolution which he did say.
But the issue here is the veracity of the quote:
Darwin said that "life can only come from life."
How many times around the mulberry bush before people admit that the quote here attributed to Charles Darwin does not appear in any of his published works or private letters and is therefore unsubstantiated?
But that is not the issue. The false quotation is Darwin said that "life can only come from life."