[jessriedel]

I think I grok that some simplifications are more useful and teachable than others, and that it's possible to accomplish useful things by simplifying (and also by misleading). But I don't think you have to be a hardcore logical positivist to think these are distinct notions from "validity". My impression is that you have psychological or statistical training, so when you used the word in your original comment I assume you know what it meant.