acuity, acumen, astuteness, clear-sightedness, keenness, penetration, percipience, perspicacity, sensitivity, understanding

appreciation, apprehension, comprehension, grasp

brain(s), braininess, brightness, brilliance, canniness, cleverness, gray matter, intellect, intelligence, judgment (or judgement), mentality, power, reason, sense, smartness, wit

discrimination, foresight, foresightedness, judiciousness, prudence, sanity

logic, rationality