 Locke knew all of these men and their work. Locke, Boyle and Newton were all founding or early members of the English Royal Society. It is from Boyle that Locke learned about atomism (or the corpuscular hypothesis) and it is from Boyle’s book The Origin of Forms and Qualities that Locke took the language of primary and secondary qualities. Sydenham was an English physician and Locke did medical research with him. Sydenham championed careful observation of disease and rejected appeal to underlying causes. Both Boyle and Newton did work on colors that did not involve micro-corpuscular explanations. Locke read Newton’s Principia Mathematica Philosophiae Naturalis while in exile in Holland, and consulted Huygens as to the soundness of its mathematics. Locke and Newton became friends after Locke’s return from Holland in 1688. It may be that in referring to himself as an ‘under-labourer’, Locke is not only displaying a certain literary modesty, he is contrasting the positive discoveries of these men, with his own attempt to show the inadequacies of the Aristotelian and Scholastic and to some degree the Cartesian philosophies. There are, however, many aspects of Locke’s project to which this image of an under-labourer does not do justice (see Jolley 1999: 15–17). While the corpuscular philosophy and Newton’s discoveries clearly influenced Locke, it is the Baconian program of producing natural histories that Locke makes reference to when he talks about the Essay in the Introduction. He writes: