In this work, Dennett's interest in the ability of evolution to explain some of the content-producing features of consciousness is already apparent, and this has since become an integral part of his program. He defends a theory known by some as Neural Darwinism. He also presents an argument against qualia; he argues that the concept is so confused that it cannot be put to any use or understood in any non-contradictory way, and therefore does not constitute a valid refutation of physicalism. His strategy mirrors his teacher Ryle's approach of redefining first person phenomena in third person terms, and denying the coherence of the concepts which this approach struggles with.