Abstract
This chapter places Descartes's microphysical explanations in the context of contemporary discussions between scientific realists and instrumentalists in the philosophy of physics. It notes that though Descartes appears to adopt the view that his accounts are true, he also downgrades them to the status of useful conjectures. He dissolves these textual conflicts appealing to the distinction between absolute and moral or practical certainty. The chapter then appeals to Descartes's use in his natural science of a complex process of reasoning that involves induction, abduction, and deduction, and also involves oblique criteria such as generality and fertility, to articulate the claim that he should be read as a scientific realist.