The question of a creator of the universe because the parameters of the universe is fine-tuned for life, is a topic of debate among theists and atheists. The concept of fine-tuning refers to the idea that the fundamental physical constants and laws of nature are set in such a way that if they were even slightly different, life as we know it would not be possible. Fine-tuning of the universe is used by proponents of theists who say the universe was intentionally designed. Atheists best argument and perhaps the only one is the multiverse theory where there exist multiple universes all with different sets of parameters, and we just happen to exist in the one (perhaps the only one) that allows life. The argument goes that if there were enough random universes, then eventually a universe like ours might arise. However, it can logically be argued that the multiverse would also require a creator, because a system that produced universes to allow one to host life, would need to be designed for the exact same reasons that a single universe that hosts life does.