Some philosophers, like Kierkegaard, find it reasonable to believe in God in their philosophical enterprise while others do not. And each group makes a compelling argument to back the stance taken. For some God is just a an abstract idea that helps them to make their point while for others, God is being who is involved in the lives of human beings in little as in great details. In the first group one can think of Aristotle, Spinoza, Kant, etc. In the second group one can think of Socrates, Plato, Augustine, Leibniz, Kierkegaard, etc.