 In the Inquiry, a methodologically pioneering work due to its extensive and rigorous use of observational data to justify claims about perception, Reid examines each of the five senses and discusses the ways in which we achieve knowledge of the world by employing them. Intellectual Powers expands his system beyond the apprehension of the world through the senses to consideration of memory, imagination, knowledge, the nature of judgment, reasoning and taste. The Active Powers examines a collection of topics concerning ethics, the nature of agency generally, and the distinctive features of human agency.