Words denoting moral prescriptions, such as the prescriptive ‘ought’, can be construed as either objective or subjective with respect to matters of fact.Footnote 1 In the objective sense, what I ought to do depends on what is actually true, whereas in the subjective sense it depends on what I believe to be true.Footnote 2 In utilitarian ethics, this distinction is closely related to that between actualism and possibilism. ‘Very roughly, an actualist claims that whether one ought to perform an action is a function of what would happen if one performed the action, whereas a possibilist says that it is a function of what could happen if one performed the action.’Footnote 3 The same distinction can be applied to other words than ‘ought’ that express moral prescriptivity.
Judith Thomson has expressed doubt that ‘ought’ has a subjective sense. Her discussion starts out from an example of the following type:
Example 1:Footnote 4 You turn on your stove in order to cook a meal that you are for some reason obligated to make. When you do this, an unexpected and extremely implausible malfunction results in an explosion in your neighbour's apartment, leading to his death.
It would be strange to claim that on this occasion you ought to turn on the stove, although this seems to follow from a subjective interpretation of ‘ought’. Thomson says:
I greatly doubt that there is such a subjective sense of ‘ought’. On those rare occasions on which someone conceives the idea of asking my advice on a moral matter, I do not take my field work to be limited to a study of what he believes is the case: I take it to be incumbent on me to find out what is the case. And if both of us have the facts wrong, and I therefore advise him to do what turns out a disaster, I do not insist that in one sense my moral advice was all the same true, though in another sense it was false.Footnote 5
Cases can also be found that are problematic for the objective interpretation of ‘ought’. Thomson mentions the example when A plays Russian roulette on B, but due to sheer luck B is not killed. The same point can also be made, perhaps somewhat more clearly, with the following example:
Example 2 (The beneficial school shooting): A desperate person shoots university students at random. By chance he happens to shoot a student who would otherwise have committed a terror attack the next day, killing thousands of people.
With an objective interpretation of ‘ought’, it would be difficult to escape the conclusion that this killing was a right act, i.e. something that the school shooter ought to perform. Hence, in this case the objective interpretation leads to a conclusion that is just as counter-intuitive as that reached with the subjective interpretation in the first example. Ordinary usage seems to vacillate between the two interpretations.
Since we have two notions of ought, can we apply Occam's razor and define one of them in terms of the other? There are of course two ways to do this. First, we can use the objective ought as the primitive notion. The subjective ought can then be defined as that which the agent believes that she objectively ought to do. Alternatively, we can use the subjective ought as primitive. The definition of the other term is then somewhat less straightforward, but at least tentatively we can define the objective ought as referring to an idealized epistemic situation in which full knowledge is available of everything that has a determinate truth-value at the time of action.
The following example introduces a further complication that has bearing on the choice between these two alternatives:
Example 3 (The indecisive terrorist): A terrorist places a bomb in the basement of a large office building. Since he believes that God acts through chance, he uses a quantum-mechanical random number generator as a triggering device. There is a 50 per cent chance that the bomb will detonate, killing thousands of people. The terrorist is convinced that if the bomb does not explode, then that is a godly sign. He has therefore left a money order in a bank in the building. If the bomb does not explode, then a large sum will be transferred to a charity. If the bomb explodes, then the money order will be destroyed and no money transferred.
Admittedly, this example is unusual since random number operators are seldom used outside laboratories. However, it is not for this reason irrelevant, since it is based on – and puts focus on – important mechanisms that are present in our everyday lives. Quantum-mechanical uncertainty is with us all the time, although we can rarely pin down exactly how it influences our lives.
When the terrorist activates the randomizer, does he do the right thing (something that he ought to do)? According to the objective interpretation, this depends on which of the following two statements is true:
(1) If he activates the random generator, then the bomb will explode.
(2) If he activates the random generator, then the bomb will not explode.
Due to the basic indeterminacy of nature, neither of these statements is true at the time of his action. Nevertheless, we have no difficulty in understanding statements about what he subjectively ought to do at the time when he chooses whether or not to activate the mechanism. Hence, a subjective ought statement can have a determinate truth-value in a situation where the corresponding objective ought statement has no truth-value, not even an unknowable one. (The example can of course be modified to ensure that the moral status of the action is indeterminate for many years.)
We can conclude from this that the truth-value of the subjective ought cannot be defined with reference to the truth-value of the objective ought.Footnote 6 To the extent that one of the two oughts is definable in terms of the other (and thus eliminable), it is the subjective ought that can be used as the primitive term.
