It can take centuries to go from “known” to “proven.”

Quoted from Call me crazy but don't try to quantify it (via bobulate):

Often the "know" category is presided over by the philosophers and the poets, the witches and the healers. The "proven" is the realm of the white lab coat. It can take centuries to go from "known" to "proven." Louis Pasteur may have discovered penicillin, but mold has been used to treat infections since the time of the ancient Egyptians. Likewise, the idea of the unconscious — that there were drives completely out of our control, and out of our sphere of awareness, working as the engine behind our behavior — used to be a joke. Now it's an accepted truth