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Published online by Cambridge University Press: 08 February 2010
The prescriptive ‘ought’ has both an objective and a subjective interpretation. In the objective sense, what one ought to do depends on what is actually true. In the subjective sense it depends on what one believes to be true. Ordinary usage seems to vacillate between these two interpretations. An example (the indecisive terrorist) is used to show that a subjective ought statement can have a determinate truth-value in situations where the corresponding objective ought statement has no truth-value, not even an unknowable one. Therefore the subjective ought is not definable in terms of the objective ought. However, definability in the other direction is not excluded by this argument.
1 Parfit, Derek, Reasons and Persons (Oxford, 1984), p. 25Google Scholar.
2 In a complete definition of the objective ought, an exception has to be made for actions performed in order to change the agent's beliefs. A physician who has incorrect beliefs in important medical matters may be morally required to take courses that a colleague with correct beliefs in these matters is not required to take. A moral objectivist can also distinguish between subjective and objective ought in another sense, namely whether the moral standard is objective or based on the agent's (or someone else's) personal views. For the purposes of the present discussion, the standard of moral assessment is assumed to be kept constant. Subjectivity or objectivity refers here to views on matters of fact, not to standards of moral appraisal.
3 Zimmerman, Michael J., ‘Risk, Rights, and Restitution’, Philosophical Studies 128 (2006), p. 297CrossRefGoogle Scholar. In another common terminology, an act is called rational if one subjectively ought to perform it and right if one objectively ought to perform it, see Smart, John J. C., ‘An Outline of a System of Utilitarian Ethics’, Utilitarianism, For and Against, John J. C. Smart and Bernard Williams (Cambridge, 1973), pp. 3–74CrossRefGoogle Scholar.
4 Modified from Thomson, Judith Jarvis, Rights, Restitution, and Risk: Essays in Moral Theory (Cambridge, Mass., 1986), pp. 177 ffGoogle Scholar.
5 Thomson, Rights, Restitution, and Risk, p. 179.
6 The following two implausible escape routes may be worth a brief mention: (i) to define the subjective ought in a way that requires that the agent has demonstrably false beliefs about the objective ought, and (ii) to make the intelligibility of subjective ought statements depend on some interpretation of quantum mechanics that tries to preserve determinism.
