Moral Arguments

When making arguments about moral acts, can you build premises around objective moral facts? Or, are all our moral claims a construct of  opinion and/or cultural constructions? Discover Magazine posted the following debate between bloggers:

You can’t use logic to derive moral commandments solely from facts about the world, even if those facts include human desires. Of course, you can derive moral commandments if you sneak in some moral premise; all I’m trying to say here is that we should be upfront about what those moral premises are, and not try to hide them underneath a pile of unobjectionable-sounding statements. 

As a warm-up, here is an example of logic in action:

All men are mortal.

Socrates is a man.

Therefore, Socrates is mortal.

The first two statements are the premises, the last one is the conclusion. (Obviously there are logical forms other than syllogisms, but this is a good paradigmatic example.) Notice the crucial feature: all of the important terms in the conclusion (“Socrates,” “mortal”) actually appeared somewhere in the premises. That’s why you can’t derive “ought” from “is” — you can’t reach a conclusion containing the word “ought” if that word (or something equivalent) doesn’t appear in your premises.

This doesn’t stop people from trying. Carrier uses the following example (slightly, but not unfairly, paraphrased):

Your car is running low on oil.

If your car runs out of oil, the engine will seize up.

You don’t want your car’s engine to seize up.

Therefore, you ought to change the oil in your car.

At the level of everyday practical reasoning, there’s nothing wrong with this. But if we’re trying to set up a careful foundation for moral philosophy, we should be honest and admit that the logic here is obviously incomplete. There is a missing premise, which should be spelled out explicitly:

We ought to do that which would bring about what we want.

Crucially, this is a different kind of premise than the other three in this argument; they are facts about the world that could in principle be tested experimentally, while this new one is not.

Read the entry here, the counterpoint here.