If, as we argued in Chapter 1, emotions influence political tolerance judgments, in spite of the long-standing hope that reason would prevail, we must take account of emotional factors. Our study must include an empirical investigation of affect if for no other reason than to better understand how reason and emotion collectively shape political judgments. But to accomplish that goal we need to have a theory that can identify which emotions matter, identify when and why they matter, and show how emotion and reason interact.

The work of a British psychologist, Jeffrey Gray, has been very influential in guiding our understanding of the functions that emotions serve (Gray, 1981,1984, 1985, 1987a, c, 1990). According to Gray's theory and research, emotions provide ongoing assessments, much as the reading provided by a thermometer tells us the temperature, or as the movement of numbers in a digital clock tells us the time. So too, Gray suggests, changes in mood report changes in ourselves and in our immediate environment.