 But as Sober and Wilson (1998) have argued with great clarity, there is no simple connection between evolutionary theory and the philosophical debate between egoism and altruism. This is because the concept of altruism that is important in evolutionary theory is quite different from the standard concept of altruism invoked in the philosophical debate. For biologists, an organism behaves altruistically if and only if the behavior in question reduces its own fitness while increasing the fitness of one or more other organisms. Roughly speaking, an organism’s fitness is a measure of how many descendants it will  have.[11]  As Sober and Wilson note, on this evolutionary account of altruism, an organism can be altruistic even if it does not have a mind capable of having beliefs and desires. Thus there can be no easy inference from biological altruism to psychological altruism. Nor does the inference go in the opposite direction. To make the point, Sober and Wilson (Ch. 10) note that natural selection might well equip humans or other psychologically sophisticated organisms with ultimate desires to foster the welfare of their offspring under certain circumstances. Organisms with these ultimate desires would be psychological altruists, though the behavior that the desires gave rise to would typically not be evolutionarily altruistic, since by helping their offspring organisms typically are increasing their own fitness. So, contrary to the presumption that evolutionary biology has resolved the debate between egoists and altruists in favor of egoism, it appears that evolutionary theory little to offer that will support that  conclusion.[12]