The human female, he insists, is far from sufficing alone for the rearing of children, since the needs of human life require many things that one person alone cannot provide.”46 For this reason, it is “in keeping with human nature that the man remain with the woman after coition, and not leave her at once, indulging in promiscuous intercourse.”47 It never dawned on Aquinas that in human pre-history, females did raise the children. This last quotation suggests, as William James and Mary Midgley have argued so cogently in the twentieth century, that human beings are creatures of multiple impulses that sometimes conflict.48 Aquinas recognized that under certain conditions, males have inclinations to form families and assist females in raising highly dependent infants. But they also have other inclinations toward promiscuity or something akin to what evolutionary ecologists call the R-strategy (procreation of a large number of offsring). In the Summa contra Gentiles, he writes that male animals desire “to indulge at will in the pleasure of copulation, even as in the pleasure of eating.” For this reason, they fight with one another for access to females and they “resist another’s intercourse with their consort.”49 Aquinas recognized the role that pateral certainty and recognition play in forming a lasting bond between a male, his consort, and their offspring: “Man naturally desires to be assured of his offspring: and this assurance would be altogether nullified in the case of promiscuous copulation. Therefore the union of one man with one woman comes from a natural instinct.”50 This is Aquinas’s rather wooden way of saying that males prefer not to unknowingly take responsibility for another male’s children. A system of monogamous bonding heightens a male’s certainty that a particular child is his and makes it more likely that he will care for his offspring and remain with the mother. Aquinas taught that fathers care for their children as a way of enhancing their own immortality, a concept similar to the theories of inclusive fitness and kin altruism. With a distinctively masculine bias typical of his day, he wrote, “Since the natural life which cannot be preserved in the person of an undying father is preserved, by a kind of succession, in the person of the son, it is naturally befitting that the son succeed in things belonging to the father.”51 Aquinas’s main source for this insight was Aristotle’s Politics.52 In one place Aristotle wrote, “In common with other animals and with plants, mankind have a natural desire to leave behind them an image of themselves.”53 These protoevolutionary theories of reproductive fitness and kin altruism led Aristotle to oppose Plato’s proposal in The Republic that civil harmony and true equality would be enhanced if a child were taken from its parents after birth and raised by the state. Parents, according to the proposal, were to be kept ignorant about which child was actually theirs. Plato argued that such an arrangement would lessen competition between families and clans, lead adults to treat all children as their own, and encourage children to relate to all grown-ups as their own parents.54 Aristotle believed that Plato’s proposal would lead to the general neglect of all children. He wrote, “That which is common to the greatest number has the least care bestowed upon it.”55 For Aristotle, parental investment comes with parental recognition that a particular child is his or hers. He thought that in Plato’s state, “love will be watery…Of the two qualities which chiefly inspire regard and affection – that a thing is your own and that it is your only one – neither can exist in such a state at this.”56 In every animal species where the father has a certain care for his offspring, the one male has but one female, as may be seen in birds, where both unite in feeding their young. On the other hand where the male animal has not the care of the offspring, we find indifferently union of one male with several females, or of one female with several males: such is the case with dogs, hens and so forth.”57 There can, of course, be too much emphasis on the role of parental certainty for producing long-term commitment to children. Qualifications of this rule apply to most couples who adopt. Such couples are highly motivated to become parents – more so than most people. Hence, they often make excellent, highly invested parents. Furthermore, evolutionary theorists tell us that we become attracted to nonkin infants partly because they activate parental potentials which have been selected and retained over the course of evolution for their relevance to children.