This interview covers James Peebles's early interest in building things and influence of father; graduate education at Princeton; mentorship with Robert Dicke; introduction to cosmology; Peebles's early questioning of the assumption of homogeneity in cosmological models and the validity of cosmological models; the simplicity of the universe; history of Dicke's suggestion to search for the cosmic background radiation; Dicke's suggestion to Peebles to work out the theoretical consequences of a hot, young universe; attitude toward the question of whether the universe is open or closed; attitude toward the inflationary universe model; problems with oscillating universe models; history and meaning of the flatness problem; attitude toward the horizon problem; reasons why horizon and flatness problems became important when they did; various reactions in the community toward the horizon and flatness problems; initial skepticism toward the inflationary universe model; reasons why the inflationary universe model has been so influential; attitude toward initial conditions in cosmology; role of observations in creating new theories; reaction to de Lapparent, Geller, and Huchra's work on large-scale inhomogeneities; change in thinking about large-scale structure; importance of balloon analogy in visualizing the expansion of the universe; use of visual images in science; relationship of theory and observation in cosmology; crisis in our theory of galaxy formation; attitude toward extrapolating physics back to the very early universe; ideal design of the universe; question of whether the universe has a purpose.