Put in this way, of course, Hegel's World Spirit sound suspiciously like an extra-material sort of being, which puts it somewhat at odds the materialist base of humanism. There is a stable, coherent, knowable self. This self knows itself and the world through reason, or rationality, posited as the highest form of mental functioning, and the only objective form.
Freedom consists of obedience to the laws that conform to the knowledge discovered by reason.
Science thus stands as the paradigm for any and all socially useful forms of knowledge. Language, or the mode of expression used in producing and disseminating knowledge, must be rational also.