If anything that exists has to have a cause, what caused god to exist? And how does anyone know that the universe hasn't simply always existed in some way or other? Green Peacemst Green Peacemst 1 second ago OK, let´s take your question no 2 first. The Big Bang theory is based on "science" itself, scientific philosophy, actually. You didn´t get Craig´s points about past infinity not being possible, and the Bord-Guth-Valenkin paper. You might like the ideas of Black Hole portals and their blowing off new Universes ideas. Those are mechanistic, and the issue means questioning the assumptions of science itself. Once you know that the Universe had a beginning, that is, a beginning where time, space, and matter-energy all came into existence. They didn´t exist before that. Physically, you might be thinking that the Universe existed as a Big Lump, and then it just exploded. They don´t see that happening. Astrophysicists trace all the space and stuff back in time, a...