After the duties which have their source directly in Nature, Pythagoras commends to his disciples those which proceed from the social state; friendship follows immediately filial piety, paternal and fraternal love; but this philosopher makes a distinction full of meaning: he ordains to honour one’s relations; he says to choose one’s friends. This is why: it is Nature that presides at our birth, that gives us a father, a mother, brothers, sisters, relations of kinship, a position upon the earth, and a place in society; all this depends not upon us: all this, according to the vulgar, is the work of hazard; but according to the Pythagorean philosopher these are the consequences of an anterior order, severe and irresistible, called Fortune or Necessity. Pythagoras opposed to this restrained nature, a free Nature, which, acting upon forced things as upon brute matter, modifies them and draws as it wills, good or bad results. This second nature was called Power or Will: it is this which rules the life of man, and which directs his conduct according to the elements furnished him by the first. Necessity and Power are, according to Pythagoras, the two opposed motives of the sublunary world where man is relegated. These two motives draw their force from a superior cause that the ancients named _Nemesis_, the fundamental decree,[285] that we name _Providence_. Thus then, Pythagoras recognized, relative to man, things constrained and things free, according as they depend upon Necessity or the Will: he ranked filial piety in the first and friendship in the second. Man not being free to give himself parents of his choice, must honour them such as they are, and fulfil in regard to them all the duties of nature, whatever wrong they might do towards him; but as nothing constrains him from giving his friendship, he need give it only to the one who shows himself worthy of it by his attachment to virtue.