In the past two weeks I’ve stumbled upon blog entries that argued for a “scientific morality”, and in doing so challenged the “is/ought thesis”, which seems to be a rite of passage to be a naturalist these days. Unfortunately, the writers misunderstand the “is/ought” thesis, and so their arguments against it fail (but both entries are interesting and worth reading, in no particular order, here and here). Both writers seem to think that the “is/ought” thesis is false because it entails that evaluative statements are not factual statements, and as statements about value are facts when they are true, the thesis is false. Indeed, what makes a statement a fact is that it is true, and so evaluative statements and descriptive statements are true if they are propositions that correspond to the world. In order for their arguments against “is/ought” to be correct it would have to be the case that the “is/ought” thesis entails that the difference between evaluative statements and descriptive statements is that evaluative statements do not describe the world, and so cannot correspond to the world in a way that would make them truth-apt propositions, and thus possible of being facts when true. But the “is/ought” thesis does not entail this at all. All that the thesis requires is that the difference between evaluative statements and descriptive statements is that evaluative statements contain evaluative terms, while descriptive statements contain no evaluative terms. It would take further argument to show that a statement containing evaluative terms cannot be truth-apt.
Today I want to contribute to this discussion of the “is/ought” gap, with the hopes that I will convince some of the truth of said gap. A further point will be to suggest that accepting the “is/ought” gap does not rule out a scientific morality.
The “Is/Ought” Gap:
The “gap” between the “is” and the “ought” is the gap in a deductive argument where there must be a leap from purely descriptive premises to an evaluative conclusion. Consider this argument:
P1. Factory-raised livestock endure much pain and suffering through the course of their lives.
P2. To eat factory raised livestock is to financially support factories that cause livestock pain and suffering through the course of their lives.
C. Therefore, it is morally wrong to eat factory-raised livestock.
This argument is not valid because the truth of the premises does not guarantee the truth of conclusion, as it seems possible that given the truth of these premises it might be false that it is wrong to eat factory-raised livestock (as evidence consider that many omnivores grant the truth of the premises but deny the conclusion). What we need is a “bridging premise” that makes the conclusion necessarily follow from the other premises. The needed premise would be “it is morally wrong to financially support factories that cause livestock pain and suffering through the course of their lives”, as we can see clearly that if eating factory raised livestock financially supports pain and suffering, and financially supporting pain and suffering is wrong, then eating factory raised livestock is wrong. But this of course is to introduce an evaluative premise into the body of argument, and so, here at least, we see that an evaluative conclusion doesn’t follow from descriptive premises unless there is an evaluative premise in the argument.
The defender of the “is/ought” thesis is prepared to press this point against all such arguments, showing those arguments with only descriptive premises that seem valid to only be valid because of an implicitly evaluative premise hidden in the argument. Of course, this method of argumentation would only be to show on a case by case basis that it is false that “is/ought” gap is false. Nevertheless, there is good reason to think the “is/ought” gap is real, because the “is/ought” gap is a moral manifestation of a general principle of logic that goes, “one cannot validly deduce a conclusion that applies a predicate P, from premises that nowhere contain that predicate. This is nothing special about evaluative predicates; it applies to any predicate whatsoever” (Michael Huemer, Ethical Intuitionism, page 74). Thus, there is a powerful argument for why the gap is real, and good evidence to support the generalization that no argument with all descriptive premises can lead to a evaluative conclusion without an implicit evaluative bridging premise.
The Consequences of Embracing the “Is/Ought” Gap:
Contrary to popular belief the consequences of accepting the “is/ought” gap are not very serious. One response to the “is/ought” gap is to note that, as it does seem that we have moral knowledge about substantive moral positions, and to do so we must have moral knowledge that is not deducible from purely descriptive premises (that is, after all, the nature of the gap), there must be some bedrock, foundational moral knowledge that is a priori. In the example given above, that a priori moral knowledge might be, “it is morally wrong to cause pain and suffering”. Indeed, if there is any a priori moral knowledge, it is likely to be about the wrongness of causing pain, as we can see on reflecting on the nature of pain as a concept that there is an impartial to-be-avoided-ness built into the concept, thus amounting to a priori knowledge seen through what is called ethical intuition (see my writings on Robert Audi or ethical intuitionism in general). I favor this response.
The other route is to accept the “is/ought” gap, and with it that evaluative conclusions cannot be deduced from purely descriptive premises, but posit that cogent inferences can be made from descriptive premises to evaluative conclusions. The Cornell realists (the original proponents of scientifically reputable moral realism in the 20th century) embrace this conclusion with Nicholas Sturgeon noting in “Ethical Intuitionism and Ethical Naturalism” that we can breach the gap with an inference to the best explanation, a method grounded in an empiricist rationale and thus being entirely consistent with common methodologies of scientific inquiry, and thereby the possibility of a scientific morality. David Brink, another influential Cornell realist writes that, “thus, the is/ought thesis leaves open the possibility […] of good nondeductive inferences between moral and nonmoral statements with, and perhaps without, the benefit of bridge premises. […] I assume that, whatever its exact specification, inference to the best explanation is a legitimate nondeductive inference pattern” (David Brink, Moral Realism and the Foundations of Ethics, page 169). The point is that we can have moral knowledge and be scientifically minded moral realists and still embrace the is/ought gap, which we have good reason to accept.
The “is/ought” gap is quite real, but scientifically minded moral realists don’t have much to fear from it. I’m not sure why they feel the need to resist it. It seems they purposefully conflate it with a metaphysical thesis concerning reductivism, and thus, the attack on the “is/ought” thesis is in the absence of successful arguments for reductivism, which seems to be the other component of “scientific realism”.