Keith is an Honorary Professor in the Philosophy Department at the University of Sheffield, a Visiting Research Fellow with The Open University, and an Adjunct Professor with the Brain and Mind Programme at the University of Crete.

Keith is best known for his theory of illusionism—the view that phenomenal consciousness, or the subjective feeling of experience, is an illusion. Rather than denying that we have conscious experiences, Keith argues that our intuitive conception of them as inherently mysterious or non-physical is mistaken.