Doxastic Voluntarism, Epistemic Rationality, and Practical Rationality
I’ve heard it said that if one’s reasons for accepting A and B are equally good such that the epistemic probability for either is 50%, then one can select to believe either option, but the selection wouldn’t be rational. I’m not a direct doxastic voluntarist, but I’m inclined to believe that one can choose in such scenarios.* However, I deny that the choice wouldn’t be rational at all.
It is commonly held that there are two senses of rationality: epistemic and practical. The former is about seeking beliefs supported by the prevailing evidence. If the evidence supports A and B at 50% each, there is no prevailing evidence; hence, neither doxastic choice would be epistemically rational.
But the selection could be practically rational. Practical rationality is a matter of selecting achievable ends and appropriate means; that is, if one intends an end which requires a particular means, then one wills the relevant means. Thus, if one does not will the means, rationality requires that he not pursue the end. As John Broome puts it: “It is commonly recognized that rationality requires you to intend what you believe is a necessary means to an end that you intend.”** R. Jay Wallace writes: “Instrumental rationality, in its most basic form, instructs agents to take those means that are necessary in relation to their given ends. In the modern era, this form of rationality has widely been viewed as the single unproblematic requirement of practical reason.”***
Suppose that the epistemic probability of A is 50%, and ditto for B. However, believing A is a necessary means for some aspect of human flourishing and believing B is not. Although opting to believe A is not epistemically rational, it is practically rational. Hence, the option is rational.
The conclusion that believing A is practically rational suggests an objection to W. K. Clifford’s rule. In The Ethics of Belief, he writes: “To sum up: it is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence.” (See page 5)
Assuming that 50/50 evidence is insufficient for belief, Clifford’s rule excludes the choice to believe A, and it excludes the choice to believe B. His rule suggests non-commitment between the two. But Clifford seems to neglect practical rationality. If it’s practically rational to believe A, then Clifford’s claim is false. His claim also faces a problem of self-refutation. Is there sufficient evidence to believe Clifford’s claim? What is that evidence? If not, the epistemic standard set by the claim precludes believing it.
*I am inclined to accept indirect doxastic voluntarism, which holds that, at least in general cases, although one cannot choose one’s beliefs on the spot (e.g., you can’t choose on the spot to believe that 2 + 2 = 97 or that square circles grow on the backyard tree), one can choose to engage in rational investigation and reflection, which can lead to one forming or discarding a particular belief of a kind open to such change.
**John Broome, “Rationality,” in A Companion to the Philosophy of Action, ed. Timothy O’Connor and Constantine Sandis (Oxford: Wiley-Blackwell, 2010), 289.
***R. Jay Wallace, Practical Reason, Stanford Encyclopedia of Philosophy, ed. Edward N. Zalta, accessed October 30, 2018, https://plato.stanford.edu/entries/practical-reason/#InsStrRat.