DISCERNER n.
One who, or that which, discerns, distinguishes, perceives, or judges; as, a discerner of truth, of right and wrong. A great observer and discerner of men's natures. Clarendon.
ACUTENESS n.
The faculty of nice discernment or perception; acumen; keenness; sharpness; sensitiveness; -- applied to the senses, or the understanding. By acuteness of feeling, we perceive small objects or slight impressions: by acuteness of intellect, we discern nice distinctions. Perhaps, also, he felt his professional acuteness…