Christian Philosophy concerns the perennial paradox of reason/revelation and philosophy/theology by reflecting on: whether philosophy has ever been «pure» i.e., free of beliefs, how Plato, Aristotle, Plotinus helped prepare for Christian philosophy, how these practiced it: Bonaventure, Guerric, Albert, Aquinas, Maritain. As monists Marcel and Whitehead confirm that philosophy cannot be faith but must remain distinct and yet dependent on it if philosophy is to be Christian. This book closes by studying how Aquinas' positions are an antidote to current trends such as Sartre's existentialism, Neo-kantian self-centered epistemology and ethics, Derrida's deconstructionism.