I haven't been following the grounding literature, so this may be old hat, in which case I will be grateful for references.
The following seems pretty plausible:
- p is fundamental if and only if p is ungrounded.
But I think (1) may be false. I will put the argument in tensed fashion, but it could also be done a bit more awkwardly in a four-dimensional setting.
Let's suppose that <I ought to respect other persons> is a fundamental moral truth. Call this truth R. But now I validly promise to respect other persons. Then R comes to be grounded in <I ought to keep my promises and I promised to respect other persons>. If (1) is true, then R continues to be true but ceases to be fundamental. That doesn't sound right. It seems to me that if R is ever a fundamental moral truth, then it is always a fundamental moral truth. After I have promised to respect other persons, R gained a ground but lost nothing of its fundamentality.
Maybe I can motivate my intuition a little more. It seems that R has a relevantly different status from the status had by S, the proposition <I ought to come to your house for dinner every night>, after I promise you to come to your house for dinner every night. Each of R and S is grounded by a proposition about promises, but intuitively the fundamentality-and-grounding statuses of R and S are different. A sign (but only a sign--we want to avoid the conditional fallacy) of the difference is that R would still be true were the proposition about promises false. Another sign of the difference is that <I ought to respect you> is overdeterminingly grounded in <I ought to respect all persons> and <I promised to respect all persons and I ought to keep my promises>, while it is false that <I ought to come for dinner tomorrow night> is overdeterminingly grounded in <I ought to come for dinner every night> and <I promised to come for dinner every night and I ought to keep my promises>. The latter is not a case of overdetermination.
The above example is controversial, and I can't think of any noncontroversial ones. But it seems plausible that we should be open to phenomena like the above. Such prima facie possibilities suggest to me that ungroundedness is a negative property, while fundamentality is something positive. Normally, fundamental truths are also ungrounded. But they don't lose their fundamentality if in some world they happen to be grounded as well.
A somewhat tempting way to keep the above intuition while maintaining the idea that fundamentality is to drop the irreflexivity of grounding and say that:
- p is fundamental if and only if p grounds p.
Then we could say that R is overdeterminingly grounded by a proposition about promises as well as by R itself, while S is only grounded by a proposition about promises and not by S. And in ordinary language we do sometimes use expressions like "p because p" to express some kind of fundamentality of p. I am not that happy with this solution, but can't think of another one that keeps the idea that fundamentality is defined in terms of grounding. Of course, one could take fundamentality to be fundamental.
