Spinoza on Freedom, Affects, and the Geometrical Method

Parts III through V of the Ethics turn from metaphysics to what Spinoza calls the affects (affectus) — the passions and active emotions of finite modes such as human beings — and to the ethical life that follows from correctly understanding them. Spinoza announces in the preface to Part III his intention to treat human actions and appetites "just as if it were a question of lines, planes, and bodies," explicitly rejecting the then-common moralizing approach of authors who "deride, bewail, or scorn" the emotions rather than seeking to understand their necessary causes; for Spinoza, since every mode follows necessarily from the nature of substance, human emotions and actions are as fully subject to natural law and rational explanation as any geometrical figure. From two primary affects, pleasure or joy (laetitia) and pain or sadness (tristitia) — understood as the mind's awareness of an increase or decrease in the body's power of acting — together with desire (cupiditas), Spinoza derives an extensive taxonomy of derivative emotions such as hope, fear, love, hatred, envy, and pity, each defined with the same formal rigor as his metaphysical propositions.