Leibniz understood that mathematics has a special place in the human search for wisdom because the things of mathematics are so determinate, and exhibit their determinate inter-relations so clearly. However, he also believed that the proper use of mathematics requires careful philosophical reflection. Leibniz recognized that while different sciences require different methodologies, no matter what special features different domains exhibit, all scientific investigation must move between mathematics and metaphysics. Mechanics, in particular, is best viewed as a middle term between mathematics and metaphysics, and so too Leibniz’s account of time. Of all the parameters involved in mechanics, time is the least tied to any specific content, even though it presents a determinate topic for scientific investigation. Thus a closer look at Leibniz’s account of time presents an especially ‘pure’ version of the interaction of mathematics and philosophy in the service of progressive knowledge.