Here’s Adam of Daylight Atheism’s reply to the questions I asked him yesterday about the difference between moral and mathematical laws, and whether either is human-independent. (He also pointed out that we’ve sparred on this point before, and you may want to refer back to the map-territory post).
I believe that mathematics and logic are discovered, rather than invented, although those terms are apt to get us bogged down in deep semantic waters.
I think it sheds more light on my position to answer in this way: As jack put it, mathematics and logic depend on objective properties of the universe that are independent of humans. Morality also depends on objective facts, but these facts aren’t independent of humans. They’re objective facts about humans: facts about what harms us and what causes us to flourish, facts which are therefore dependent on the kind of creatures we are. If our evolution had taken another path, if we were a very different kind of creature than we are, the rules of morality that apply to us would be different; and if we never existed at all, there would be no true facts about us and therefore morality would not exist.
Technically mathematical facts aren’t independent of the objects they describe, either. It’s not a property of math-writ-large that the angles of a triangle sum to 180 degrees, it’s just a property of triangles. (Or, more precisely, a property of triangles in Euclidean geometry). It would be true of Euclidean triangles whether or not any existed in the physical world or there were any people anywhere to think of them.
Once you name something a triangle or mention some of it’s qualities, you’ve pulled in many other properties, including some you might not yet have discerned (the sum of any two sides of a triangle exceeds the length of the remaining side, etc). Technically you’ve encapsulated them all once you said “three-sided polygon” but it takes work and discovery to understand what logically follows and why.
Describing what a thing is (its essence) constrains its telos (the ends it’s directed toward). There can be true facts about non-existent things — for example: unicorns have four legs, whether or not they exist. It’s our ability to describe and predict the properties of things that may not exist that lets us come up with ways to test whether they’re real or categorize them at all. If we weren’t humans, or if humans ceased to be, then their would still be facts about hypothetical rational animals, even if there was no one to hypothesize about them.
So, yes, moral law is dependent on humans insofar as the obligations of humans are different from those of dogs, but I think this kind of hairsplitting distracts from the bigger question about cultural relativism and changing norms. I don’t want to get too far into the weeds on the very abstract “what if humans were different and so the moral way to treat them was different” question, because I think the moral law is actually fairly stable over a number of conceivable variations in human culture and human biology. I’ll explain why in a second post, which will also be a chance to start making good on my promise to explain where I think C.S. Lewis gets it right.
(And, lo! that post is now up)