it takes one to know one; a thief knows a thief; the wolf knows what the ill beast thinks
Proverb meaning that people of the same kind, especially those with similar vices or expertise, understand each other best. Often used when someone's insight into another's bad behavior reveals their own similar nature.
He spotted the scam right away—it takes one to know one, I guess.
As the saying goes, 'a thief knows a thief,' so I can see right through his schemes.
Standard kanji form of the proverb.
Literally 'a snake knows the way of a snake.' The exact origin is uncertain, but it is a traditional Japanese proverb reflecting the idea that those of the same kind understand each other's ways.