Here's some controversy for your afternoon! Enjoy!
So, that "babies" argument...
At first I thought it was merely unconvincing, but I'm starting to think it is actually an argument that is better avoided.
First, does anyone know if we have Epicurus on record using it? I know Cicero puts it in the mouth of Torquatus. I'd guess Lucretius probably used it...you can find anything in that poem! I'm curious to see what the real pedigree of the argument is.
I said earlier, a theory is required before you can interpret facts. I meant "required" literally. It's not just a nice-to-have. You must have one, and if you think you don't have one, you're deceiving yourself - you just haven't made your theory explicit. If "theory" sounds too Platonic, substitute "assumptions".
To give a (hopefully) non-controversial example, one of the assumptions in any kind of "look to nature" argument is that nature is the right place to look. I don't think I've ever heard anyone explain why nature is the right place to look. It's taken for granted. I'm fine with that, because nature IS usually a good place to look, and there aren't too many alternatives.
The argument that we should look to babies reasons (!) that they are in a kind of pure, or uncorrupted state of nature, so should serve as an ethical norm. An obvious corollary is that we shouldn't look to the behavior of more mature humans because they have been corrupted. It's not always clear what the corrupting influence is - I could turn that into another rant.
My problem is with the implicit assumption that any deviation from the original state of nature is necessarily for the worse.
That is a profoundly destructive belief. I feel comfortable calling that idea evil - if not in an absolute sense, certainly in the sense of being anti-human. And not only anti-human, but anti-life of any sort. Life is growth, which is change. The absence of change is death.
Now, I'm not saying the "babies" argument itself is evil...it's a reasonable thing to point to as a piece of evidence. But it has in it a seed of an idea that could be taken in some really bad directions.