In On What Matters, Derek Parfit argues that we sometimes have objective reasons to have certain desires or aims. I find this to be a metaphysical claim, and other philosophers (such as Michael Smith) have said similar things.

According to Reasons Fundamentalism, there is a fundamental metaphysical relation that holds between facts, on the one hand, and beliefs, desires, aims, and actions, on the other. This relation holds when the fact in question gives a reason for the belief, desire, aim, or action. The relation is metaphysically fundamental, or so the suggestion goes, because we cannot define what it is for a fact to give a reason for some belief, desire, aim, or action, in terms of other facts; we cannot analyze the concept of a fact’s giving a reason for some belief, desire, aim, or action, in terms of other concepts; we cannot reduce the property of giving a reason for some belief, desire, aim, or action, to some other property; and so on.

– Michael Smith (2017) Parfit's Mistaken Meta-ethics

Is there any alternative, non-metaphysical interpretation of Parfit's objectivism? Because the metaphysical undertones of his work makes it impossible for me to take the whole thing very seriously and I have extreme difficulty finding motivation to make the effort and actually read his full 3 volumes. I know a lot of respectable philosophers admire Parfit, and I like his older and more famous thought experiments regarding personal identity and the repugnant conclusion, but I just cannot buy his metaphysical metaethics. The only alternative explanation is that when he says "sometimes it is the objects of our desires of aims that give us reasons to have such desires or aims", he is simply proposing a linguistic convention. In that sense he wouldn't be claiming to have discovered an a priori truth about the nature of the universe, but rather he would be inventing a convention and advocating in its favor. However, the language he uses throughout the book seems to indicate that he doesn't think of his statements as proposing conventions:

Rather than proposing a new moral theory, I shall try to learn from some existing theories, hoping to get somewhat closer to the truth.

– Derek Parfit (2011) On What Matters

If somebody could show me that "he is on to something", and that he is not being metaphysical, perhaps that would help me to find the motivation to read the entire On What Matters (I only read part one of volume one).

  • The claim that we have objective reasons to believe that energy is conserved is no more or less metaphysical. That does not make it a priori. It is an empirical generalization, and well confirmed as such, but projecting energy onto reality and speaking of it as a real entity is metaphysics. Yet, empirical facts give us reasons to believe energy conservation. "Objects of our desires or aims give us reasons to have such desires or aims" can be seen as another such generalization, and Parfit's "learning from some existing theories" as reaching for what has been confirmed by ethical experience.
    – Conifold
    Aug 27, 2020 at 7:13
  • I don't think it's exactly the same. Sure, science relies on the metaphysical premise that there is an objective external reality, but then it only makes empirically verifiable claims about this reality. The conservation of energy was inferred via empirical observation. To say that "facts gives us objective reasons to…" is not an empirically verifiable claim relying on an accepted metaphysical premise. It seems to be a metaphysical claim relying on language, and that I think is a fundamental difference.
    – Ariel
    Aug 28, 2020 at 7:29
  • To me, "facts give us objective reasons to" looks like a trivial inference from "facts are objective claims" (by definition, assuming realism for their existence), and "claims can be used as reasons". "Objects of our desires give us reasons to have them" is an empirical surmise from entities/events out there moving us to do things. Either way, I do not see much metaphysics there beyond generic realism. I think I do not follow your point about language and conventions, how are they relevant here at all? And how can a metaphysical claim rely on language?
    – Conifold
    Aug 28, 2020 at 12:15


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