The first premise is relatively uncontroversial, and is rooted in the metaphysical principle that out of nothing, nothing comes. The denial of the first premise, although strictly logically possible, is metaphysically unactualizable. By definition, nothing has no potentialities. Thus, it is impossible for something to arise out of nothing, for how can its existence be actualized if the potential is not there? The truth of the causal premise is additionally supported by our everyday experience. If the causal premise were false, then it is quite odd as to why we don't observe things coming into existence uncaused and out of nothing in our everyday experience. Presumably, nobody lives their life worrying about the possibility of an elephant suddenly appearing out of nothing in their living room. Writes Craig:
"Why is it only universes that can come into being from nothing? What makes nothingness so discriminatory? There cannot be anything about nothingness that favors universes, for nothingness does not have any properties. Nothingness is the absence of anything whatsoever. As such, nothingness can have no properties, since there literally is not anything to have any properties. Nor can anything constrain nothingness, for there is not anything to be constrained."
The second premise of the kalam cosmological argument is supported by both philosophical and scientific arguments. Arguments under the former category involve showing that the existence of an actually infinite number of things is metaphysically impossible. If the universe never began to exist, then its past duration would be actually infinite. Since actual infinities cannot exist, then the past duration of the universe must have been finite, implying that the universe must have begun to exist. Even if one grants that it is possible for an actual infinite to exist, it still cannot be formed by successive addition, and henceforth the