In this paper we suggest a revisionist perspective on two significant figures in early modern life science and philosophy: William Harvey and John Locke. Harvey, the discoverer of the circulation of the blood, is often named as one of the rare representatives of the ‘life sciences’ who was a major figure in the Scientific Revolution. While this status itself is problematic, we would like to call attention to a different kind of problem: Harvey dislikes abstraction and controlled experiments (aside from the ligature experiment in De Motu Cordis), tends to dismiss the value of instruments such as the microscope, and emphasizes instead the privileged status of ‘observed experience’. To use a contemporary term, Harvey appears to rely on, and chiefly value, ‘tacit knowledge’. Secondly, Locke’s project is often explained with reference to the image he uses in the Epistle to the Reader of his Essay, that he was an “underlabourer” of the sciences. In fact, despite the significant medical phase of his career, Locke’s ‘empiricism’ turns out to be above all a practical (i.e. ‘moral’) project, which focuses on the delimitation of our powers in order to achieve happiness, and rejects the possibility of naturalizing knowledge. When combined, these two cases suggest a different view of some canonical moments in early modern natural philosophy.