In Posterior Analytics II 19 Aristotle likens the way in which sense perception gives rise to knowledge of the universal to the way in which one soldier’s ceasing his flight from the enemy leads other soldiers to do the same ‘heôs epi archên êlthen.’ Although the remark seems intended to characterize knowledge as the end result of an accumulative process, the concluding reference to ‘a starting point’ or archê has no clear meaning. I argue that the phrase can be plausibly (...) understood in light of Aristotle’s explanation of how a single calm thought can spread calm to other thoughts (Problems 917a29-33) and a single cloud can serve as a starting point (archê) for a revival of stormy weather (Problems 941a9-13). In addition, Aristotle elsewhere (e.g. Generation of Animals 788a13-16) speaks of the archê as the person or thing which initiates a process. Thus, when one soldier’s stopping causes another soldier to stop, this process can continue ‘until they come to the one who initiated the process.’ . (shrink)