While on a run in Maine, I happened to be thinking about the Is/Ought problem as well as fallacies. I was also thinking about bears and how many might be about in the woods, but that is another matter.
This problem was most famously put forth by David Hume. Roughly put, the problem is how one might derive an “ought” from an “is.” Inspired by Hume, some folks even go so far as to claim that it is a fallacy to draw a moral ought” from a non-moral “is.” This is, unlike the more common fallacies, rather controversial. After all, it being a fallacy or not hinges on substantial matters in ethics rather than on something far less contentious, like a matter of simple relevance. While I will not address the core of the matter, I will present some thoughts on the periphery.
As I ran and thought about the problem, I noted that people are often inclined to make moral inferences based on what they think or what they do. To be a bit more specific, people are often inclined to reason in the following two ways. Naturally, this could be expanded but for the sake of brevity I will just consider thought and action.
The first is belief. Not surprisingly, people often “reason” as follows: I/most people/all people believe that X is right (or wrong). Therefore people ought to do X (or ought to not do X). For example, a person might assert that because (they think that) most people believe that same-sex marriage is wrong, it follows that it ought not be done. This is, obviously enough, the fallacy of appeal to belief.
The second is action. People are also inclined to infer that X is something that ought to be done (or at least allowed) on the basis that it is done by them or most/all people. For example, a person might assert that people ought to be able to steal office supplies because it is something everyone does. This is the classic fallacy of appeal to common practice.
While there are both established fallacies, it seems somewhat interesting to consider whether or not they are potentially Is/Ought fallacies when they involve deriving an “ought” from the “is” of belief or action.
On the one hand, it is rather tempting to hold that they are not also Is/Ought errors. After all, it could be argued that the error is exhausted in the context of the specific fallacies and there is no need to consider a supplemental error involving deriving an “ought” from an “is.”
On the other hand, these two fallacies seem to provide a solid foundation for the Is/Ought error that is reasonably well based on established logic. This suggests (but hardly proves) that there might be some merit in considering the Is/Ought fallacy in a slightly different light-that it can actually be regarded as a special “manifestation” of various other fallacies. Or perhaps not.
What people believe is X, so X is good: Appeal to belief.
What people do is X, so X is good: Appeal to common practice.