There is no reason on the idea that you can’t get an ought from an is to accept the idea that you can’t get and ought from an is. In fact, the whole concept of epistemic obligation goes out the window if the is/ought dichotomy is real.
This is a strong claim, so let’s unpack it.
Say we both agree that the is/ought dichotomy (or fact/value dichotomy) is true: the condition really obtains that you can’t get an ought from an is.
We both believe it’s true, but our attitudes about our beliefs diverge wildly.
You believe that it’s true and you affirm that it’s true (in the way that we typically mean when we say we believe something). Your belief and your assent to what you believe are aligned.
I, on the other hand, believe that it’s true but I decline to assent to is as true. I prefer to act like it isn’t true at all.
It seems like there is something wrong with my attitude. But what is it?
If you say that in rejecting the is/ought dichotomy even though I believe it I’m flouting my epistemic duty to assent to that which I rationally believe to be true, I will counter that doing so is exactly what the is/ought dichotomy allows me to do.
After all, if existence creates no obligation, as is the case according to the is/ought dichotomy, then why am I obligated to affirm the is/ought dichotomy merely because it is true (i.e., that the condition it describes actually obtains in reality)?
Or, for that matter, why am I obligated to assent to anything that is true? In what sense do I have any epistemic obligation at all if you can’t get an ought from an is?
If I am not bound by epistemic obligation, then accepting the truth of what merely exists must be a matter of preference. (That I ought to affirm the is/ought dichotomy certainly exists as a proposition, but the mere existence of that proposition creates no actual obligation on my part if the is/ought dichotomy is real).
Instead of epistemic obligation, we are left with epistemic preference.
As a consequence I can, without violating the conditions of the is/ought dichotomy, simply reject the is/ought dichotomy as a matter of preference and instead assert a rival and incompatible theory: moral realism, which not only cannot be said to suffer from the same undercutting self-referentiality that afflicts the is/ought dichotomy, but must be accepted as just as valid an expression of epistemic preference as affirmation of the is/ought dichotomy itself.
And the only way around that obligation—the obligation implicit in the is/ought dichotomy to accept affirmation of the rival and incompatible theory of moral realism as valid—is to reject the law of noncontradiction and to believe that a proposition can be both true and false at the same time and in the same sense; namely, that the existence in reality of the condition that you can’t get an ought from an is somehow creates an ought: an epistemic obligation to affirm the is/ought dichotomy against its incompatible rival, moral realism.
So the is/ought dichotomy leaves us in a peculiar situation: to believe it implies we must deny that there exists a real obligation to affirm it, yet even to do that is to accept the burden of an obligation that the theory denies can be derived from the reality the theory itself insists upon.
Conclusion: the is/ought dichotomy is seriously self-undercutting and ought to be rejected.
If the is/ought dichotomy is a positive truth claim that purports to tell us about the state of affairs that obtains with regard to moral epistemology, then by its own terms we are under no epistemic obligation to affirm it, or to assent to any other truth claim for that matter, regardless of its relationship to what we rationally believe to be true.
NOTE: Updated 7/13/2022