Think of 'perspicacity' as mental clarity that cuts through confusion like a sharp knife.

Mental Sharpness

Use 'perspicacity' to describe someone who notices things that are not obvious to others.

Observation Skill

'Perspicacity' often refers to the ability to think critically and make intelligent deductions.

Critical Thinking

 of islands beyond the visible horizon, simply by watching the reverberation of waves across the hull of their vessel, knowing full well that every island group in the Pacific has its unique refractive pattern that can be read with the same perspicacity with which a forensic scientist would read a fingerprint.