Spinoza's rationalism engenders a drive for unification. Because sharp breaks in reality are, for him, inexplicable and unintelligible, Spinoza's commitment to the principle of sufficient reason (hereafter: "the PSR") – the principle that for each thing that exists there is an explanation – dictates a rejection of such breaks. In Spinoza's philosophy of mind, the crucial unifying notion is that of representation. Thus, volitions, emotions, and also affirmations and negations, i.e., judgements, are all reducible to representations of one kind or another, representations of certain objects or states of affairs. For Spinoza ideas, representations, as such and by their very nature, are judgements or affirmations and, by their very nature, are volitions and affective states. There is no sharp break in Spinoza between representations and mental states such as judgements and volitions.