A second major branch of developmental cognitive theory also has its roots in Ancient Greece, and is usually traced to Aristotle, who was Plato’s student. Aristotle agreed with Plato and his followers that reliable knowledge consists of abstract ideas, but disagreed about the impossibility of these being derivable from sense experience. Aristotle was an acute and practised observer — as a naturalist who systematically catalogued the features of living things; as an embryologist who followed the development of chicks in their eggs; and as an anatomist who dissected human bodies. From these many activities Aristotle had acquired immense knowledge: different from sense experience in the sense of being universal or abstract, as the Platonists had insisted; but nonetheless derived from it. Far from being an illusion, not to be trusted, sense experience seemed to him to be the very meat of knowledge. In direct contradiction with his former master, Aristotle propounded a connection between facts and general principles.