Theism and Explanation - Appeared-to-Blogly

Appendix 153
we assume is a “myth,” since human beings often act irrationally. But he
adds that the rationality principle “works very well” for the simple reason
that “we are pretty rational.” 31 So the simplest explanation of the utility of
the rationality principle would seem to be that it is (more or less) true: we
often do act rationally. And when we become aware that we are not acting
rationally, we try to adjust our beliefs or actions so as to act more rationally.
32 In this sense, the rationality principle is at least an approximation to
the truth. 33 Remember, too, that we adopt this principle only as a presumption;
it is defeasible. We may fi nd that the agent in question reasons badly
about how she should act. Or we may fi nd that she is not, in fact, acting in
accordance with the intention she has formed, since she suffers from weakness
of will (Appendix 2.3).
What does “rationality” imply, in this context? In Chapter 5 (5.3.3), I
identifi ed three criteria of rationality in action, although my list makes no
claim to be exhaustive. A fi rst and minimal requirement is that of consistency.
Given certain beliefs and desires, we would expect a rational agent
to act in a way which is consistent with those beliefs and desires. If we
posit that a particular agent desires to express affection for her partner,
this would explain her purchasing a gift. Her purchasing a gift would be
consistent with her desire to express affection. It would not be consistent
with her stirring rat poison into his coffee. A closely related requirement
is that of perceived effi cacy. Given a particular goal, a rational agent will
act in a way which (if her beliefs were true) would bring about that goal.
She may, of course, be mistaken. She may think that purchasing a boldly
striped tie for her beloved will successfully convey her feelings of affection,
when in fact he loathes ties in general, let alone striped ones. But given her
(mistaken) beliefs, this might still be a rational way to act. Finally, there
is the requirement of effi ciency. Given a posited goal, we would expect a
rational agent, all other things being equal, to choose the most effi cient
way of attaining that goal. If she intends to go to the supermarket, then we
would expect her to take the most direct route, unless she has some other
goals whose attainment demands otherwise.
A.2 EXPLANATION AND ARGUMENTS
To what point has this discussion led? Intentional explanations explain an
agent’s behaviour by positing a particular reason for acting, an intention
which (it is claimed) motivates her behaviour. What our explanation needs
to show is that, given this intention, it would be reasonable for the agent
to act in this way. 34 This means that our attempt to offer an intentional
explanation may be defeated. There may be no intention that we can plausibly
attribute to this agent that would make her behaviour rational, even
by her own lights. In this situation, we would have to seek some other kind
of explanation.