The ability to judge
discernment, discrimination, taste, penetration, shrewdness, sapience, sagacity, understanding, knowledge, sense, good sense, wit, keenness, sharpness, critical faculty, reason, reasoning power, rationality, rational faculty, acumen, intuition, acuteness, perception, incisiveness, intelligence, awareness, sophistication, ingenuity, experience, profundity, depth, brilliance, mentality, subtlety, intellectual power, critical spirit, capacity, comprehension, sanity, lucidity, levelheadedness, clearheadedness, mother wit, quickness, readiness, grasp, apprehension, perspicacity, perspicuousness, soundness, genius, reach, range, breadth, astuteness, prudence, discretion, wisdom, sagesse (French), savvy*, gray matter*, brains*, a good head*, horse sense*; see also acumen.
Antonyms stupidity*, simplicity, naiveté.
The act of judging
decision, consideration, appraisal, examination, judging, weighing, sifting, assaying, determination, inspection, assessment, estimation, diagnosis, probing, appreciation, evaluation, interpretation, study, review, contemplation, analysis, inquiry, inquisition, inquest, search, quest, pursuit, scrutiny, exploration, reconnaissance, close study, observation, exhaustive inquiry, regard; see also study 2.