Few questions are argued with as much philosophical rigor and as much at stake: whether a perfect, personal being grounds and explains the universe, or whether the universe and its order need no such explanation. The ontological argument, which goes back to Anselm, reasons from the concept of God alone, without appeal to experience: a maximally perfect being would not merely happen to exist, so its existence is held to follow from what it is. Cosmological arguments trace the chain of causes back to a first cause; design arguments infer a designer from the order and apparent purposiveness of nature, and in their modern versions from the fine-tuning of physical constants; their critics answer that regularity and complexity are explicable without invoking anything beyond the natural world.
The dispute bears on other questions too: what counts as an adequate explanation, what kind of evidence religious experience provides, and what follows for ethics if there is or is not a source of value beyond human agreement.