The Constant Wanderer

1. Perception; understanding; knowledge.
2. The range of vision.
3. View; sight.

He was to make several important discoveries, the most significant being that infantile paralysis was caused not by germs, as cerebrospinal meningitis had been, but by a mysterious agent just then emerging into the ken of science.
-- James Thomas Flexner, Maverick's Progress

So we are predisposed -- if not preprogrammed -- to accept tales of animals who display human motives, understanding, reason, and intentions. It takes a far greater imagination to conceive the possibility that a dog's mental life may assume a form that is simply beyond our ken.
-- Stephen Budiansky, If a Lion Could Talk

Libussa, the youngest, particularly beautiful, unworldly and serious, was able to see what was hidden from other people's ken and to prophesy.
-- Peter Demetz, Prague in Black and Gold

Ken is from Middle English kennen, from Old English cennan, "to declare, to make known."