  The perfectionist language Spinoza uses is important for an understanding of the basis for ethics that he finds in psychology. Here, however, it may be understood in terms of striving. An increased power to persevere in being is for Spinoza a transition to greater perfection and a decreased power is a transition to lesser perfection (see IIIp11, the end of IV Preface, and especially III, Definitions of the Affects, III, Exp.). So, although this generalization is complicated by Spinoza’s definitions that refer passions either to parts of the body or to the body as whole, joy is the passion one experiences in the transition to an increased power to strive, and sadness is the passion one experiences in the opposite transition. Spinoza thus provides, in his account of the affects, the basis for an explanation of how it is that introspection into our conscious experience of desire might fail to bring us accurate knowledge of our own psychological processes. Our conscious experience in forming our desires, has an emotional component: we experience joy and sadness and varieties of these. But we may be unaware of why we feel joy or sadness or why, really, we desire what we desire. So Spinoza writes repeatedly, in the context of his criticisms of teleological reasoning and the introspective experiences of free will or mind/body causation (e.g., at IIIp2s): “men are conscious of their actions and ignorant of the causes by which they are determined.”