Manners make the man / Manners maketh man
Today this expression broadly means that your mannerisms and characteristics make you who you are, that is to say people are judged by their manners and conduct. But in its earliest use, as manners maketh man, it likely had a broader meaning--that manners make us human - that politeness and etiquette are what prevent us from falling into savagery.
The Random House Dictionary of America's Popular Proverbs and Sayings traces manners maketh man to the middle of the 14th century but without citing a specific reference. The earliest reference BookBrowse could find was in the work of William Horman who was headmaster of Eton and then Winchester in the late 15th century. Winchester College still retains "manners makyth man" as its motto, as does New College, Oxford, both of which were founded by William of Wykeham, Bishop of Winchester, in the 14th century.
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All alone or in twos, the ones who really love you
Walk up and down outside the wall
Some hand in hand, some gather together in bands
The bleeding hearts and the artists make their stand
And when they've given you their all
Some stagger and fall, after all it's not easy
Banging your heart against some mad bugger's wall
(Roger Waters)