This chapter explores John Sergeant’s criticism of Le Grand’s account of the causation of cognition. Le Grand claims that “nervous motions” provide an occasion for the soul to form relevant ideas. The chapter describes some of the metaphysical objections Sergeant raises against his opponent and explores the charge of enthusiasm levelled against Le Grand. According to Sergeant, for nervous stimuli to occasion a mental state cannot be for the stimuli to cause the state in any way. For as Le Grand himself had claimed in his Dissertatio de ratione cognoscendi, “every effect is similar to its cause.” According to Sergeant, Le Grand is committed to the general view that, at any moment of time, a substance is in the state it is in because God willed that it was in that state. A recurrent theme in Sergeant’s anti-Cartesian writings is the worry that the Cartesian theory of ideas is conducive to “enthusiasm”.