Emotion researchers have identified about a couple dozen discrete emotional states that exist along intensity continua, such as apprehension-fear-terror, or annoyance-anger-rage. Some emotions are blends of simultaneously activated emotions, such as trust and fear blending into submission, or trust and joy blending into love.

Researchers have proposed several lists of primary emotions. Damasio's list includes fear, anger, disgust, surprise, sadness, and happiness. Some emotional states imply social relationships—such as sympathy, guilt, jealousy, envy, and gratitude. So it's been complex and confusing. Looking for Spinoza is Damasio's successful attempt to simplify and clarify things—including the identification of specific brain systems that process emotion.

Think of being in a state of current contentment (mental equilibrium, bodily homeostasis). Our sensory and/or memory systems detect an emotionally competent stimulus from inside or outside our body—a danger or an opportunity.

An immediate analysis of the relevant environment and the current state of our body/brain follows. The basic concerns: What are my current levels of alertness, strength, and energy? Are they such that I'm capable of successfully confronting the challenge—and further, am I motivated to do it? If the analysis is optimistic, Damasio suggests that various emotions that signal a joyful state will emerge (such as joy, anticipation, trust). On the other hand, if the analysis is pessimistic, emotions that signal a sadness state will emerge (such as fear, anger, grief). We'll thus move confidently forward towards a strategy that will resolve the challenge or we'll warily avert it.