What IS good, and how do we determine it?

[Randy Carson]

Some atheists who believe that objective moral right and wrong really do exist, a position also called moral realism, say they simply know that these moral truths exist, and that’s good enough for them. For example, Walter Sinnott-Armstrong answers the question, “Why is it wrong to cause harm without a good reason?” by saying, “It just is, don’t you agree?” Erik Wielenberg, in his book Value and Virtue in a Godless Universe, writes, “Of the ethical states of affairs that obtain necessarily, at least some are brute facts.”

Is it fair for atheists merely to assume that moral truths exist as unexplained brute facts? Luke Muehlhausesr, the founder of Common Sense Atheism, writes:

Many atheists see to think moral realism is obvious, and easy to prove. I disagree. Consider the claim we moral realists are making. We generally claim there are invisible properties in the world not detectable y our usual tools of science, properties of an entirely different sort than the usual “is” facts of science. These are mysterious “ought” facts, and there is great disagreement about what they are or how we know them. Now that is a strong claim. An extraordinary claim, we might say. And extraordinary claims require extraordinary evidence, right?

Muehlhauser then examines two reasons atheists give to believe in the existence of objective moral truths. The first is that atheists just “know” or “experience” the truth of the wrongness of things such as rape. The second reason is that until objective moral truths are disproven, the atheist is justified in believing them. Muehlhauser continues:

Do those arguments look familiar? They should. They are the exact same arguments atheists reject when they are given for the existence of God. Atheists are skeptical of these arguments when given for the existence of God, but they are credulous and gullible toward these arguments when you replace the word “God” with another mysterious thing called “moral truths.”…It would be hypocritical for me to reject subjective experience and popular consensus as evidence for God while at the same time accepting subjective experience and popular consensus for moral realism.

(Luke Muehlhauser. “Many Atheists are Hypocrites about Morality,” Common Sense Atheism, May 9, 2010. Available online at: http://commonsenseatheism.com/?p=8859)