Following a recent trend in the field of the history of philosophy and medicine, this paper stresses the necessity of recognizing empiricism’s patent indebtedness to the sciences of the body. While the tribute paid to the Hippocratic method of observation in the work of Thomas Sydenham is well known, it seems necessary to take into account a trend more critical of ancient medicine developed by followers of chemical medicine who considered the doctrine of elements and humours to be a typical example of the idols that hinder the improvement of medical knowledge and defend the necessity of experimentation (comparative anatomy, dissection, autopsy, chemical analysis of bodies). In light of the fact that modern discoveries (blood circulation, the lymphatic system, theory of fevers) resulted in a “new frame of human nature,” they developed a critical reading of ancient empiricism. As a consequence, we can distinguish between two distinct anti-speculative traditions in the genesis of philosophical empiricism. The first (which includes Bacon, Boyle and Willis) recommends an active investigation into nature and refers to the figure of Democritus, the ancient philosopher who devoted himself to the dissection of beasts. Defenders of this first tradition refuse point-blank to be called ‘empiricists’, a label which had a very negative meaning during the seventeenth century, when it was used to dismiss charlatans and quacks. The other tradition (including Sydenham and Locke), stressing as it does the role of description and observation, is more sceptical of the ability of dissection or anatomy to give us access to causes of diseases. This later tradition comes closer to the definition of ancient empiricism and to the figure of Hippocrates.