“Whatever begins to exist has a cause” is an inference from things inside the universe, where beginning means rearranging existing matter. The universe beginning from nothing is a different kind of event, and we have no experience of it.

This is the strongest challenge to the first premise. The reply is that the premise is not an empirical generalization but a metaphysical principle: things do not come into being uncaused from literally nothing, because nothing has no properties, including the property of producing things. If the principle failed, there would be no reason anything does not pop into existence uncaused all the time. Critics answer that quantum events look uncaused, which the Krauss exhibit addresses. The premise is defensible, and it should be described as a philosophical principle rather than a law of physics.