The idea I was operating under was that “compare to” means to liken and “compare with” means to examine to discover differences as well as likenesses. Therefore, you might compare someone to a summer’s day, but you’d discuss how your first-quarter earnings compare with last quarter’s.
Bossy language commentators have, for years, peddled this rule. Here’s Theodore M. Bernstein’s 1965 “The Careful Writer.”
“The choice of ‘to’ or ‘with’ to follow ‘compare’ is not a matter of indifference. When the purpose is to liken two things or to put them in the same category, use ‘to.’ When the purpose is to place one thing side-by-side with another to examine their differences or their similarities, use ‘with.’”
If you follow this guideline, you get good results. To say “Shall I compare thee to a summer’s day,” as Shakespeare did, simply sounds better than “Shall I compare thee with a summer’s day.” Putting a modern spin on this phrase doesn’t change this: “Can I compare you to a summer’s day” sounds better than it would with “with.”
So what’s the problem? It’s that Bernstein and a host of others who laid down this law went too far. Just because one preposition sounds better than another doesn’t mean one of them is wrong.
Prepositions have a unique function in the language. Unlike other parts of speech that are governed by strict laws of syntax, prepositions are sometimes governed solely by idiom.
