Or, in other words, the principle of "garbage in, garbage out" applies.
But if your claim is that rationality is independent of culture (which, as I've already noted, is rubbish, since the idea of what is rational and irrational changes with cultural zeitgeist, unless you have some claim to objective rationality which I don't) then we can't use a static methods of rationality to judge the goodness of a particular goal, which is obviously context-dependent. So if not rationality, then what? I suggest critical thinking in place.
That's what I was trying to say in my previous comment. Even if you execute rational reasoning perfectly, if you start with garbage input, you end up with garbage output. If you intrinsically value something horrible, e.g. murdering kittens, rationality isn't going to tell you to not do it; on the contrary, it'll suggest the most effective means of doing that.
> But if your claim is that rationality is independent of culture (which, as I've already noted, is rubbish, since the idea of what is rational and irrational changes with cultural zeitgeist, unless you have some claim to objective rationality which I don't)
I meant it in the same way in which 2+2=4 or F=ma are independent of culture. Of course the work of discovering rational reasoning was happening over long time, with important contributions in Ancient Greece and earlier. But we've only recently managed to get some good formal tools applicable to real-life problems of reasoning, namely probability theory.
> then we can't use a static methods of rationality to judge the goodness of a particular goal, which is obviously context-dependent. So if not rationality, then what? I suggest critical thinking in place.
What do you suggest this "critical thinking" is made of? As for judging the goodness of a particular goal - you can decompose that into parts that can be judged rationally on their effectiveness (and consistency), and parts that have to be judged morally.
How do you feel about the fact that was is rational and irrational (indeed our whole meta-rational basis) has changed in time according not to new discoveries but merely the movement of the cultural zeitgeist[0]? What about the differences between instrumental reason (and rationality), technological rationality in which modern technology changes what we see as rational (see Marcuse) and rationality of ends, rather than just the means?
My point is that we can't simply say "rationality" as if it's a fixed tool we can use so easily, at least, we can't use it without also considering the current ideological context in which we are using it. Surely you admit there are different rationalities, such as economic rationality, which would seem to eschew any human factor that does not count towards profit efficiency?
[0] https://en.wikipedia.org/wiki/Eclipse_of_Reason_(Horkheimer)