In man (as the only rational creature on earth) those natural faculties that aim at the use of reason shall be fully developed in the species, not in the individual.
Reason in a creature is the capacity to enlarge the rules and purposes of the use of his resources far beyond natural instinct. It does not recognize any boundary to its projects. It does not develop instinctively but requires trials, experience, and information in order to progress gradually from one level of understanding to the next. Therefore every man would have to live excessively long in order to learn how to make full use of all his faculties.
Or, if nature has set man a short term of life (as is, in fact, the case), then (perhaps) nature requires an endless procession of begettings of which one transmits its enlightenment to another, in order finally to push the genus of humankind to that level of development that is appropriate to the purpose of nature. This time must, at least theoretically, be the target of the endeavors of man, because other wise the natural faculties would have to be considered largely pointless and in vain. This would vitiate all practical principles, as it would suggest that nature, the wisdom of which serves as a principle in judging all other natural arrangements, would have to be suspected of childish play when it comes to man.