If anyone is to doubt the spiritual and religious nature of the ancient Greeks all they need to do is read Phaedo. Plato has given us an account that not only schools us on the nature of the soul, but teaches us that grace and divinity are things readily attainable for the human being. I find it easy to see Western religion, particularly Christianity, in the writings of the Greeks. But the commonalities seem much more prevalent in Phaedo. The introduction by Benjamin Jowett is a useful tool for anyone coming to this with little experience in Plato's writings. Plus this is free for Kindle. It is a quick read that promises the depth of an epic. I highly recommend Phaedo.