Oppy on Moral Arguments (Part 9): The Argument from Convergence

This post is part of my series on Graham Oppy's discussion of moral arguments. For an index, see here.


The Argument Stated
The ninth argument covered by Oppy is a neglected historical oddity. It is attributed to Henry Sidgwick (who did not endorse it) and is known as the argument from convergence. Take a look:

• (P1) What I have most reason to do is what will best secure my own happiness.

• (P2) What I have most reason to do is what morality requires.

• (P3) If there is no moral government of the universe, then what will best secure my happiness is not always what morality requires.

• (C1) Therefore, there is a moral government of the universe.

• (C2) Therefore, there is an orthodoxly conceived monotheistic god.

This is actually a pretty profound argument, and more deserving of consideration than the tawdry argument from the need for justice (which is similar in content). I think it neatly summarises certain opinions and intuitions that we have about the nature of morality. In particular, it captures the tension that most people see between self-interest and morality.  


Anyway, there is no need to wax lyrical on it for too long, we need to know whether the argument is successful.


Analysis
Sidgwick rejected the conclusion of this argument for one simple reason: he thought it more likely that there was a fundamental irreconcilable tension in the faculty of practical reason, than that there was a God to reconcile them. I tend to agree.

Oppy notes, as I did a moment ago, that the argument equivocates between prudential reason and moral reason. One way to resolve the tension is to reduce moral reasons to prudential reasons or vice versa. Many secular theories of morality do this. For example, Hobbes reduced moral reasons to prudential reasons of a particular sort.