The content of the pseudo-Pythagorean writings results from a blending of Platonic and Aristotelian doctrines, which is typical of Platonism, beginning in the first century BC. Platonic doctrines are mediated by the academic tradition, which shapes the basic orientation of the treatises towards systematization and classification. Pythagoreanism became inextricably entwined with Platonism and came to exercise a far wider influence than its actual standing should have permitted. The theory of principles plays a fundamental role in all spheres of knowledge, but its very formulation contains innovative elements, which make the pseudo-Pythagorean system more than simply a repetition of early Academic doctrines. The Aristotelian doctrines are integrated within a Platonizing system: Aristotle's hylomorphism is thus interpreted in the light of the doctrine of Ideas, identified with Aristotelian Forms, and traced back to the two fundamental principles. The same reduction of Aristotelian notions to two principles occurs in cosmology, ethics and politics.