 Theophrastus (c. 371–287 BCE), who followed Aristotle as the head of the Lyceum, is critical of the Pythagorean approach. He observes that we may find quantitative regularities in things other than musical intervals, yet we still consider these things as different from musical entities. This, he argues, must be due to the fact that intervals and melodies are essentially something other than numbers (Barker 1990: 111–114; Lippman 1964: 157–160; Barker 2007: chapter 15).