perspicacious (adj) - showing keen mental perception and understanding [pur-spi-kay-shuhs]
BREAKDOWN: PER- (through) + SPIC- (to look) + -ACIOUS (inclined to)
perspicacity is keenness of mental perception and understanding; discernment
See also: circumspect, conspicuous, spectral, speculate
“People are likely to conform to the choice of the majority, even if it is plainly wrong, and that they do so not only through a desire to fit in, but also because their very perceptions are skewed towards those of the group. Whole societies can be affected to the extent that their most perspicacious minds are unable to see what would be obvious to even a relative simpleton at another time in history.” —Andrew Lynn
