23. Now Pythagoras declared that the unbegotten monad was the principle of the universals[82] and the parent of the dyad and of all the other numbers. And he says that the [Sidenote: p. 270.] monad is the father of the dyad and the dyad the mother of all engendered things (and) a bearer of things begotten. And Zaratas,[83] also, the teacher of Pythagoras, calls the one father, but the two, mother. For the dyad has come into being from a monad according to Pythagoras, and the monad is masculine and first, but the dyad female and second. From the dyad, again, as Pythagoras says, (come) the triad and the other numbers one after the other up to 10. For Pythagoras knew that this 10 is the only perfect number.[84] For (he saw that) the 11 and 12 were an addition to and re-equipment of the decad, and not the generation of some other number. All solid bodies beget what is given to them from the bodiless.[85] For, he says, the Point which is indivisible is at once a point and a beginning of the bodies and the bodiless together. And, he says, from the point comes a line, and a superficies extended in depth makes, he says, a solid figure. Whence the Pythagoreans have a certain oath as to the harmony of the four elements. And they make oath thus:-- [Sidenote: p. 271.] “Yea by the Tetractys handed down to our head A source of eternal nature containing within itself roots.”[86] For the beginning of natural and solid bodies is the Tetractys as the monad is of the intelligible ones.[87] But that the Tetractys gives birth to the perfect number as among the intelligibles the (monad) does to the 10, they teach thus. If one beginning to count, says 1, and adds 2, and then 3 in like manner, these will make 6. (Add) yet another (_i. e._) 4 and there in the same way will be the total 10. For the 1, 2, 3 and 4 become 10, the perfect number. Thus, he says, the Tetractys will in all things imitate the intelligible monad having been thus able to bring forth a perfect number.