A new arrival, Kouran, recently challenged our conventional use of the label "rational" to describe various systems. The full thread is here, and it doesn't summarize neatly, but he observes that we often use "rational" in the context of non-intellectual, non-cognitive, etc. systems, and that this is an unconventional use of the word.
Unsurprisingly, this led to Standard Conversation Number 12 about how we don't really use "rational" to mean what the rest of the world means by it, and about instrumental rationality, and etc. and etc. In the course of that discussion I made the observation a couple of times (here and here) that we could probably substitute some form of "optimal" for "rational" wherever it appears without losing any information.
Of course, status quo bias being what it is, I promptly added that we wouldn't actually want to do that, because, y'know, it would be work and involve changing stuff.
But the more I think about it, the more it seems like I ought to endorse that lexical shift. We do spend a not-inconsiderable amount of time and attention on alleviating undesirable side-effects of the word 'rational,' such as the Spock effect, and our occasional annoying tendency to talk about the 'rational' choice of shoe-polish when we really mean the optimal choice, and our occasional tendency to tie ourselves in knots around "rationalists should win". (That optimized systems do better than non-optimized systems is pretty much the definition of "optimized," after all. If we say that rational systems generally do better than irrational systems, we're saying that rational systems are generally optimal, which is a non-empty statement. But if we define "rational" to mean the thing that wins, which we sometimes do, it seems simpler to talk about optimized systems in the first place.)
There's precedent for this... a while ago I started getting out of the habit of talking about "artificial intelligences" when I really wanted to talk about superhuman optimizing systems instead, and I continue to endorse that change. So, I'm going to stop using "rational" when I actually mean optimal. I encourage others to do so as well. (Or, conversely, to tell me why I shouldn't.)
This should go without saying, but in case it doesn't: I'm not proposing recoding anything or rewriting anything or doing any work here beyond changing my use of language as it's convenient for me to do so.