But we have to “teach” the human abstracting power to man. We know since Piaget and Vygotsky that this abstracting power of man, called conceptualization, has a genesis and a growth trajectory that is different for every individual due to their environments, hence their educations.
A teacher must be an expert in helping other people in their developing their conceptualizations. Without conceptualization there is no abstract thinking, hence no abstraction(s).
Experts of any subject just cannot do that because they are locked up in their subject and not in the teaching project that considers the students as active and independent actors in the process. Experts make students hyper passive: listen and swallow and then repeat.