Parfit, Derek - Ch 5 Rationality

04/27/2012

On What Matters, Vol 1 Ch 3, Oxford University Press 2011


First two paragraphs lay out the relation between reason-giving facts and beliefs, which offer apparent reasons. When beliefs are true, then B not only has apparent reason to act, but real reason. B acts rationally when acting on apparent reasons. This is different from causal dependence, on which beliefs desires depend. Author lays out the nexus of beliefs, desires, reasons and rationality on pg112-3. Author rejects the view that it is irrational to have a desire iff it is based on an irrational belief. Author argues that it is a belief's content (pg113) that makes it rational or irrational. In other words, if the content of the belief would support the desire rationally, then the desire is rational, regardless of whether the belief is true (pg119). In some ways, a desire is rational when it is properly supported by a belief (whether that belief is rational or irrational). In other ways, not. Author works on hammering this out (pg115-7). Author concludes that there is epistemic irrationality, but that does not get transmitted over into desires, which can only have practical irrationality. A key distinction for author is that practical reasoning results in voluntary acts, but we have non-voluntary responses to epistemic reasons (pg118). 

With meta-beliefs about normativity, the same division might not work (pg119). Author considers the case of Scarlet, Crimson, and Pink (pg120). All three have "true believes about what it is like to be in agony and in slight pain, and about personal identity, time and all the other relevant non-normative facts." Scarlet prefers agony on any Tuesday vs pain on any other day of the week, Crimson prefers agony tomorrow vs any shorter pain today, and Pink prefers pain tomorrow over slightly smaller pain today. Author argues that Scarlet and Crimson are irrational, though practically rational by matching their preferences up to their beliefs (pg121). Pink is also irrational because his recognition of the irrelevance of time is correct, yet Pink still picks the pain tomorrow. However this is outweighed by having "rational beliefs about reasons" (pg122).

Next author considers the case of whether it makes any difference whether Scarlet or Crimson are subjectivists about reasons. For author, the answer is no: they are still irrational. However, it is not irrational to be a subjectivist (pg124). Author further claims that equating "rational" with "maximize expected utility" is a definitional claim, not a substantive one (pg125). Author considers other ways of using the term "rational". An interesting case is inconsistent desires. To author, they are not irrational, though acting on them both may be (pg127-8).