One Berkeleyan case for idealism, recently developed by Robert M. Adams, relies on a seeming disparity between our concepts of matter and mind. Thomas Reid’s critique of idealism directly challenges the alleged disparity. After highlighting the role of the disparity thesis in Adams’s updated Berkeleyan argument for idealism, this chapter offers an updated version of Reid’s challenge, and assesses its strength. What emerges from this historico-philosophical investigation is that a contemporary Reidian has much work to do to transpose her objections to Berkeley into good objections to Adams’s argument.