Guide For the Perplexed - Lecture 69: Part 2 Chapters 20b and 21

Rambam explains clearly Aristotle's opinion that everything is the way it is because it has to be, and that it has always been this way. This means that even God had to make the universe the way it is. He also explains that once you say that the world is eternal and not created, no amount of word games can change the fact that an eternal universe means it had to be this way.