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Conclusion

In this chapter we have showed that a single approach–game theory, with the help
of evolution and learning–can explain many of our moral intuitions and ideologies.
We now discuss two implications.

Group Selection. Our chapter relates to the debate on group selection, whereby
group level competition and reproduction is supposed to occasionally cause indi-
viduals to evolve to sacrifice their own payoffs to benefit the group (e.g., Wilson,
2006). One of the primary pieces of evidence cited in support of group selection is
the existence of human cooperation and morality (Fehr & Fischbacher, 2003; Fehr,
Fischbacher, & Gächter, 2002; Gintis, Bowles, Boyd, & Fehr, 2003; Haidt, 2012;
Wilson, 2010, 2012), in particular: giving in one-shot anonymous laboratory experi-
ments, intuitively sacrificing one’s life for the group (jumping on the grenade), and
contributions to public goods or charity. However, we have reviewed an alternative
explanation for these phenomena that does not rest on group selection. It also yields
predictions about these phenomena that group selection does not, such as that peo-
ple are more likely to cooperate when they are being observed and there is variance
in the cost of cooperation. The approach described here also explains other phenom-
ena, such as categorical norms and ineffective altruism. These lead to social welfare
losses, which is suboptimal from the group’s perspective. The categorical norm
against murder, for example, leads to enormous waste when keeping alive, some-
times for years, those who have virtually no chance of a future productive life.

Admittedly, despite their inefficiencies, these moral intuitions do not rule out
group selection, since group selection can be weak relative to individual selection.
But it does provide a powerful argument that group selection is unnecessary for
explaining many interesting aspects of human morality. It also suggests that group
selection is, indeed, at most, weak. One example that makes this especially clear is
discrete norms. Recall that we argued that continuous norms are not sustainable
because individuals benefit by deviating around the threshold. Notice that this ben-
efit is small, since the likelihood that signals are right around the threshold is low.
Group selection could easily overwhelm the benefit one would get from deviating
from this Nash equilibrium, suggesting group selection is weak (i.e. there are few
group-level reproductive events, high migration rates, high rates of “mutation” in
the form of experimentation among individuals, etc.).

Logical Justification of Moral Intuitions. In each of the applications above, we
explained moral intuitions without referring to existing a priori logical justifications
by philosophers or others. Our explanation for our sense of rights does not rely on
Locke’s “state of nature.” No argument we gave rests on God as an orderly designer,
on Platonic ideals, on Kant’s concepts of autonomy and humanity, etc. What does
this mean for these a priori justifications? It suggests that they are not the source of
our morality and are, instead, post hoc justifications of our intuitions (Haidt, 2012).

To see what we mean, consider the following analogy. One might wonder why
we find paintings and sculptures of voluptuous women beautiful. Before the

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