John Broome

Practical reasoning is a process of reasoning that concludes in an intention. One example is reasoning from intending an end to intending what you believe is a necessary means: 'I will leave the next buoy to port; in order to do that I must tack; so I'll tack', where the first and third sentences express intentions and the second sentence a belief. This sort of practical reasoning is supported by a valid logical derivation, and therefore seems uncontrovertible. A more contentious example is normative practical reasoning of the form 'I ought to φ, so I'll φ', where 'I ought to φ' expresses a normative belief and 'I'll φ' an intention. This has at least some characteristics of reasoning, but there are also grounds for doubting that it is genuine reasoning. One objection is that it seems inappropriate to derive an intention to φ from a belief that you ought to φ, rather than a belief that you ought to intend to φ. Another is that you may not be able to go through this putative process of reasoning, and this inability might disqualify it from being reasoning. A third objection is that it violates the Humean doctrine that reason alone cannot motivate any action of the will. This paper investigates these objections