My question is, what is the BGV theorem? and what exactly does it say? I was watching A debate on cosmology where William Lane Craig uses the Borde, Guth and Vilenkin theorem to say the universe had a beginning. I was wondering if someone could possibly explain the case of the BGV theorem and what it says? Does this theorem make other cosmologies such as the Hawking-Hartle less likely than one that had a beginning? If this subject has already been answered, could someone refer me to a link? Thanks so much if you are able to help out :) ! Mentor note: edited to remove debate video reference.