I argued in chapter 2 that thinking should be evidence based, but it should now be clear that it is inevitably emotion based as well. One of the central problems of rationality is how to combine these two essential facets of human thought. Shakespeare asked in The Merchant of Venice: “Tell me where is fancy bred, Or in the heart or in the head?” My answer is that thinking needs to integrate cognition and emotion to be fully effective, and we have the brain mechanisms that perform such integration well, at least much of the time. Let us now see how such integration occurs when people make decisions.