It might be worth noting that we don't need to rely on this particular book as a source for this distinction. It is essentially congruent with the necessary/con

It might be worth noting that we don't need to rely on this particular book as a source for this distinction. It is essentially congruent with the necessary/contingent distinction in philosophy. Other expressions of it include the strategy/tactics distinction and the nomothetic/idiographic distinction. The idea is based on the very ancient observation that phenomena involve both general laws and specific circumstances.