In this comment on the article by Papanicolaou, we introduce the concept of methodological determinism and discuss the scientific status of the concept of free will. We argue that determinism is an implicit heuristic assumption of modern science, dating back to Newton’s optics. Papanicolaou acknowledges that instances of free will being an illusion have been corroborated. We add that the proposition of free will determining behavior is unfalsifiable. It is, therefore, a metaphysical proposition and not a scientific hypothesis