This chapter reviews some important themes in contemporary emotion science. It is useful to distinguish two kinds of emotional causes: cognitive and non-cognitive. Molecular or coarse-grained, many psychologists assume that cognitive states in some form are necessary for emotion elicitation. The most obvious non-cognitive elicitors of emotions are perceptual states. Pure cognitive theorists can make little sense of the idea that emotions are caused by evaluative cognitions and constituted by something else. Emotions influence both behavior and cognitive processes. Emotions can influence what we think about and they can influence how we think. One can recognize some emotions by their facial expressions, and this can even be done unconsciously. Proponents of basic emotions often try to identify and expand their lists of basic emotions by looking for a set of cross-culturally identifiable faces. Historically, emotions have been regarded as irrational forces that interfere with reasoning.