It is likely that, under natural conditions, selection for fitness and good feelings are closely coupled. There would, under most circumstances, be no evolutionary advantage for an animal to feel good when its fitness was poor or threatened and, likewise, generally nothing to be gained by feeling bad when fit. In fact, there would be strong selection pressure against such mismatches of feelings and fitness. Pain must hurt enough to serve its purposes such as the guarding of damaged tissues and the provision of sharp lessons about things to be avoided, but not so much that it unnecessarily interferes with other body-maintenance functions such as eating and avoiding predators. Natural selection probably ‘scrutinizes’ the intensities of pleasures and pains very closely and keeps them tightly linked to health and evolutionary fitness.