to me, if someone were considered perspicacious, they would be expected to have great deductive and logical reasoning skills, finding out important facts by logical deductions--Sherlock Holmes is an excellent example of perspicious (note, Perspicacity (noun) is related here) Astute--to me has a greater meaning of praising one's general intelligence and intellectual abilities, i.e. good students are often said to be "astute learners" Perceptive to me refers to someone who pays attention to every detail in their environment. Importantly, although these words are distinct in their implications, they are often used interchangeably when such implications are not intended or important, although I would say that perspicacious is certainly found more in formal writing than in everyday conversation. astute and perceptive in particular could be used to mean the same thing. Logically, they words at a deep level carry subtle differences and are independent. For example, if someone is perspicacious, I would expect them to also be astute and perceptive, though it is possible for an astute person not to be perspicacious, i.e. not to reach the probable conclusions from deduction.