Mutation is the ultimate source of all variation present within a population . . . without mutation, there would be eventually be nothing for natural selection to select, and evolution would halt.

Perhaps you meant that inheritance and differential reproduction through time are the non-random processes that transform variation generated by random mutation into adaptations . . . ? I would agree with that.

By 'accident', Fred refers to the perspective that there is no universally defined (by a supreme intelligence) meaning to life. This notion is very upsetting to Fred and prompts him to cite great minds of the past that, in their dying years, produced platitudes about the necessity and inevitability of a divine creator.