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Validity and Practical Reasoning

Published online by Cambridge University Press:  30 January 2009

David Mitchell
Affiliation:
Birkbeck College, London

Extract

It has been argued by several writers that practical reasoning is capable of a kind of validity that is unlike the validity which theoretical reasoning can possess. One can gain an initial impression of this view's appeal, as well as of its content, by seeing how it could issue from analytical reflection upon the idea that actions, decisions and intentions all can be, and frequently are, reasonable. An inviting first step in such reflection is to say that for a certain intention, say, to be reasonable on a certain occasion is, roughly, for it to be true that a person could come to have that intention as a result of reasoning well about what to do. One might then add the further thought that, so far as regards what it is for a piece of reasoning to be well done, reasoning falls into at least two basic kinds: reasoning about what to do differs generically from reasoning about what is the case. The view which I mentioned at the outset can now be seen as a specific proposal regarding where this difference lies: reasoning about what to do has distinctive validity-conditions not shared by reasoning about what is the case.

Type
Research Article
Copyright
Copyright © The Royal Institute of Philosophy 1990

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References

1 Compare Binkley, R., ‘A Theory of Practical Reason’, Philosophical Review 74 (10 1965), 423.CrossRefGoogle Scholar

2 Harman, G., Change In View (Cambridge, Mass.: MIT Press, 1986), 11.Google Scholar

3 See further below, p. 485.

4 Kenny's main expositions of his approach are in ‘Practical Inference’, Analysis 26 (01 1966), 6575Google Scholar, and Chapter 5 of Will, Freedom and Power (Oxford: Blackwell, 1975)Google Scholar. My page-references will be to the virtual reprint of the latter in Practical Reasoning, Raz, J. (ed.) (Oxford University Press, 1978)Google Scholar. Kenny gives a briefer restatement of his position in The Metaphysics of Mind (Oxford University Press, 1989), 4345.Google Scholar

5 The complex property stands to K-validity as entailing the conclusion does to deductive validity; how many premises there are matters similarly. Compare Pears, D. F., Motivated Irrationality (Oxford University Press, 1984), 122123.Google Scholar

6 Compare Aune, B., Reason and Action (Dordrecht: D. Reidel, 1977), 128.CrossRefGoogle Scholar

7 Kenny refers to these conditions on 75–76, 78–79, and 67 respectively.

8 I do not say ‘… then there must be some premise that it is unreasona ble to accept’. That would be to assert rather more, since it might con ceivably be reasonable to do one thing and reasonable to do another but not reasonable to do both. This becomes clear if one notes the equivalence just now stated, and calls to mind the behaviour of the possibility operator in modal logic.

9 Compare Castaneda, , The Structure of Morality (Springfield, IL.: Charles C. Thomas, 1974), 124.Google Scholar

10 Op. cit. note 2, 12.

11 See Aristotle, , Movement of Animals 7, Nicomachean Ethics 7.3.Google Scholar

12 Certain points which Michael Bratman makes about the general role of intention in reasoning also count significantly, but not decisively, against (i)'s validity. See his Intention, Plans and Practical Reason (Harvard University Press, 1987), 154–144.Google Scholar

13 It will not be necessary here to decide exactly how ‘negation’ is to be interpreted outside the field of theoretical reasoning.

14 Contrast the discussion at the end of section 3 (pp. 488–489) concerning the woman's belief about her nephew's age. There it was the permitting of beliefs which was at issue; here it is the requiring of them.

15 Op. cit. note 6, 163–164; op. cit. note 2, 14.