The basis for Rahner's theology is that all human beings have a latent ("unthematic") experience of God in any experiences of meaning or "transcendental experience." It is only because of this proto-revelation that recognizing a specifically special revelation (such as the Christian gospel) is possible. The philosophical sources for Rahner's theology include Thomas Aquinas, read from the aspect of contemporary continental philosophy. Rahner attended lectures by Heidegger in Freiburg.