“The mind undergoes many changes, and can pass sometimes to a state of greater perfection, sometimes to a state of lesser perfection. These passive states of transition explain to us the emotions of pleasure and pain. By pleasure the mind passes to a greater perfection. By pain the mind passes to a lesser perfection. Further, the emotion of pleasure in reference to the body and the mind together I shall call stimulation( titillato), the emotion of pain in the same relation I shall call suffering.” Spinoza