And from this sense of necessary all the others are somehow derived; for as regards the compulsory we say that it is necessary to act or to be acted on, only when we cannot act according to impulse because of the compelling force, which implies that necessity is that because of which the thing cannot be otherwise; and similarly as regards the conditions of life and of good, when in the one case good, in the other life and being, are not possible without certain conditions, these are necessary, and this cause is a kind of necessity.