In recent years, a large amount of scholarship has been written about St Thomas Aquinas’s views on free will and determinism. This paper is an attempt to bring some Thomist views of libertarian free will into dialogue with analytic philosopher Peter van Inwagen and his ‘mysterianism’ about free will. The thesis of this paper is that Thomist libertarians about free will are committed to Peter van Inwagen’s mysterianism about free will. The paper intends to accomplish this aim by showing how recent accounts of Thomist libertarianism cannot defeat the intuitive strength of van Inwagen’s ‘Replay argument’. The significance of this conclusion is that some Thomists are committed to mysterianism and that mysterianism is a legitimate position a Thomist can hold. This also provides evidence that the Thomist tradition can grow and be nourished by engagement with contemporary analytic philosophy.

In this paper I present an interpretation of du Bois-Reymond’s thesis on the impossibility of a scientific explanation of consciousness and of its present importance. I reconsider du Bois-Reymond’s speech “On the limits of natural science” (1872) in the context of nineteenth-century German philosophy and neurophysiology, pointing out connections and analogies with contemporary arguments on the “hard problem of consciousness.” Du Bois-Reymond’s position turns out to be grounded on an epistemological argument and characterized by a metaphysical skepticism, motivated by the unfruitful speculative tendency of contemporary German philosophy and natural science. In the final sections, I show how contemporary research can benefit from a reconsideration of this position and its context of emergence, which is a good vantage point to trace open problems in consciousness studies back to their historical development.