  The conclusion that no intuitive or demonstrative knowledge of substances is possible for us, their real essences and necessary connections being out of reach, places Locke at a crossroads. One path is skepticism, the view that without certainty, no knowledge of substances is possible at all. He rejects that path, denying that hyperbolic doubt could be genuine for either the self (E IV.ix.2, pp. 619–20) or for external objects (E IV.xi.3, p. 631). The other path, the one he follows, involves lowering the bar by admitting a third kind of knowledge, one that lacks certainty: sensitive knowledge. (A recent, in-depth examination of how justified Locke is, both in avoiding skepticism and in his position on sensitive knowledge, may be found in Priselac 2016.)