  With the publication of Newton’s Principia, implying as it did the possibility of unmediated action at a distance, gravity becomes the most nettlesome phenomenon for the orthodox version of the corpuscular hypothesis, which includes a proviso of contact action. Locke is initially sympathetic to the proviso, writing in the first three editions of his Essay, “How bodies operate one upon another…is manifestly by impulse and nothing else. It being impossible to conceive that body should operate on what it does not touch.” (E II.viii.11, editions 1–3) Yet for the fourth edition, he replaces that claim about how bodies do operate with one about how we can conceive of them operating: “How Bodies produce ideas in us is manifestly by impulse, [this being] the only way which we can conceive Bodies [to] operate.”(E II.viii.11, edition 4). He also omits a clause appearing in II.viii.12 of previous editions that denied unmediated action at a  distance.[20] These subtle emendations reflect a dramatic shift, one expressed directly in his correspondence with Stillingfleet.