142. We must look, then, for other evidence. From what has been said, it will be clear that we cannot safely take Plato as our guide to the original meaning of the Pythagorean theory, though it is certainly from him alone that we can learn to regard it sympathetically. Aristotle, on the other hand, was quite out of sympathy with Pythagorean ways of thinking, but took a great deal of pains to understand them. This was just because they played so great a part in the philosophy of Plato and his successors, and he had to make the relation of the two doctrines as clear as he could to himself and his disciples. What we have to do, then, is to interpret what Aristotle tells us in the spirit of Plato, and then to consider how the doctrine we arrive at in this way is related to the systems which had preceded it. It is a delicate operation, no doubt, but it has been made much safer by recent discoveries in the early history of mathematics and medicine. Zeller has cleared the ground by eliminating the purely Platonic elements which have crept into later accounts of the system. These are of two kinds. First of all, we have genuine Academic formulae, such as the identification of the Limit and the Unlimited with the One and the Indeterminate Dyad;[768] and secondly, there is the Neoplatonic doctrine which represents it as an opposition between God and Matter.[769] It is not necessary to repeat Zeller’s arguments here, as no one will any longer attribute these doctrines to the Pythagoreans of the fifth century. Footnote 768: Aristotle says distinctly (_Met._ Α, 6. 987 b 25) that “to set up a dyad instead of the unlimited regarded as one, and to make the unlimited consist of the great and small, is distinctive of Plato.” Zeller seems to make an unnecessary concession with regard to this passage (p. 368, n. 2; Eng. trans. p. 396, n. 1). Footnote 769: Zeller, p. 369 sqq. (Eng. trans. p. 397 sqq.).