Locke has often been hailed as the father of an empiricism that provided a philosophical basis to natural science in the Age of Enlightenment. In this article his empiricism is compared with that of the little known Dutch Aristotelian professor Gerardus de Vries. There are striking parallels between Locke's brand of mechanist empiricism and the pragmatic and flexible Aristotelianism of De Vries. These parallels put strictures on both the archaic character of the Aristotelianism embraced by De Vries and on the modern and forward-looking character of Locke's philosophy of science.