If something ends in 'ist' or 'ism' it probably isn't rational. But then, perfect rationality is only possible if you can keep the irrational aspects of the universe out of your personal reality...
Humanitarianism.
Orthodontist.
Egalitarianism.
Industrialist.
Magnetism.
Psychologist.
Stoicism.
Virologist.
Capitalism.
Neurologist.
Formalism.
I could list dozens more.