In one version of the Kalaam argument, Bill Craig argues against forming an infinite past by successive addition by asking something like this: Why would someone who had been counting down from infinity have been finished today rather than, say, yesterday? This argument puzzles me. After all, there is a perfectly good reason why she finished today: because today she reached zero and yesterday she was still on the number one. And yesterday she was on one because the day before she was on two. And so on.
Of course, one can object that such a regress generates no explanation. But then the Kalaam argument needs a Principle of Sufficient Reason that says that there must be explanations of such regressive facts and an account of explanation according to which the explanations cannot be found in the regresses themselves. And with these two assumptions in place, one doesn’t need the Kalaam argument to rule out an infinite past: one can just run a “Leibnizian style” cosmological argument directly.
