I have defined rationality for myself. I struggled with this concept, because I consider myself rational despite holding beliefs that self proclaimed leaders in a so called "Rationality Movement" consider irrational.
For instance: Sam Harris, who I believe considers himself rational, claims I can't truly make choices. I believe I can truly make choices. I consider myself rational. Can we both justifiably consider ourselves rational and disagree on such a fundamental proposition?
I believe we can, provided we define rationality carefully. I have defined rationality as: how we measure the alignment of our choices with our values.
I considered that the word 'rational' contains the root 'ratio' and thus involves comparison between two things (as forming a ratio between two numbers provides a relative measurement). Then I wondered, on what basis do we form this comparison?
I believe economists use this definition, and they choose profit or utility as their value (base of comparison). I dislike their brand of rationality because I perceive it as leading to greed. But I concede that they act rationally given their values.
I guess that Sam Harris values alignment with Western science more than I do. Thus he finds it rational to fit his beliefs into a mechanistic view of the universe, whereas I find it rational to keep my beliefs unrestricted from any specific model of reality because I value freedom and openness.
I bet I value harmony more than Sam Harris, since Sam speaks against other people's beliefs. I believe he acts rationally, in doing so. And I believe I act rationally in not doing so.
In conclusion I will never to judge another person's rationality until I know their value system. Better yet, I will never judge another person's rationality, and instead use their actions to deduce their values assuming their rationality.