Common sense is quite rare.

The line is typically used to express a skeptical, satirical view of human judgment: what people call “common sense” is neither widely shared nor reliably applied. Read in a Voltairian key, it also implies a critique of social conformity and received opinion—many confidently invoke “common sense” to justify prejudice, superstition, or lazy thinking, while genuine practical reason is uncommon. The aphorism’s sting lies in its paradox: if sense were truly “common,” it would be abundant. As a database entry, it functions best as a general maxim about the scarcity of clear, independent reasoning in public life.

“Common sense is not so common.”
“Common sense is very uncommon.”
“Common sense is the least common of all the senses.”