 Although Malebranche had his share of admirers and imitators, he also had his share of critics. The theory of Vision in God was subjected to severe and sometimes bitter attacks by some of his contemporaries, especially Cartesians such as Arnauld and Régis who saw themselves as defending the legacy of Descartes against a corrupting influence. Fortunately for us, Malebranche was eager to defend himself and his replies to criticisms often help elucidate and amplify his original doctrine, as stated in the first edition (1674) of the Search After Truth. In some cases, these replies are quite extensive. Although the dispute with Arnauld ranged over other topics, and was originally sparked by theological differences, it lasted some 11 years and occupies several volumes (four of Malebranche’s, two of Arnauld’s) of their collected works. Some of Malebranche’s critics were dismissive of his doctrine. ‘[Vision in God] is an opinion that spreads not and is like to die of itself, or at least do no great harm,’ John Locke was reported as saying three days before his death (quoted in Cranston 1957, 478). Malebranche, however, could be equally disparaging of his opponents. To his critic Simon Foucher, he quipped: ‘When one criticizes a book, it seems to me necessary at least to have read it’ (OC 2:496). But once the dust from the ad hominems settled, several important philosophical issues became apparent. We shall begin here by discussing objections to the doctrine that were prevalent in Malebranche’s own time and his replies to them. We’ll focus on internal criticisms, that is, objections that purport to expose incoherencies, unsound arguments, and inconsistencies with larger aspects of his philosophy (as opposed to complaints, for example, about his Cartesian infidelities). Toward the end of this section, we shall examine a few objections that have been raised by recent commentators.