know

know it's not what you know, it's who you know modern saying stressing the importance of personal influence, late 20th century.
know the ropes be thoroughly acquainted with the way in which something is done, an expresssion deriving from the days of sailing ships, when skill in handling ropes was essential for any sailor.
know thyself proverbial saying, late 14th century; inscribed in Greek on the temple of Apollo at Delphi; Plato in Protagoras ascribes the saying to the Seven Sages, the seven wise Greeks of the 6th century bc to each of whom a moral saying is attributed.
to know all is to forgive all proverbial saying, mid 20th century. In the early 19th century the French writer Mme de Stäel (1766–1817) in Corinne (1807) has, ‘Tout comprendre rend très indulgent [To be totally understanding makes one very indulgent]’, and the actress Ellen Terry (1847–1928) writes in The Story of My Life (1908), ‘I had taken a course for which all blamed me, perhaps because they did not know enough to pardon enough—savoir tout c'est tout pardonner.’
what you don't know can't hurt you proverbial saying, late 16th century; an informal version of where ignorance is bliss, 'tis folly to be wise.
who knows most, speaks least the most knowledgeable people are often the most discreet; proverbial saying, mid 17th century.
you never know what you can do till you try often used as encouragement to the reluctant; proverbial saying, early 19th century.
you should know a man seven years before you stir his fire used as a caution against over-familiarity on slight acquaintance; proverbial saying, early 19th century.

See also not know a B from a battledore, know how many beans make five, know a hawk from a handsaw, more people know Tom Fool, necessity knows no law, it takes one to know one at take.