  Locke has been widely hailed for providing an epistemological foundation for the experimental science of his day, articulating the new, probabilistic form of knowledge appropriate to it.  But while he is in important respects a devotee of that new science, there are also significant tensions in his thought.  He stands behind its experimental methods as he targets the earlier, speculative or rationalist philosophies, for methodologies and epistemological expectations unsuited to natural philosophy.  He also frequently appears to embrace the new science’s corpuscular hypothesis, whose powers and minute particles figure prominently in his attempt to understand why we cannot hope for demonstrative certainty about natural phenomena.  Yet the new science’s methodology was evolving. Just how far did Locke travel with that evolution, and what aspects of his thought prevented him from going further?  As for the corpuscular hypothesis, what exactly was his stance toward it?  He frequently speaks of particles and powers as if they belonged to established knowledge, and yet in explaining the hypothesis’ flaws, he seems to consider them fatal.  This article will mainly emphasize the second of those related questions, though both have spurred scholarly investigation and debate.