Nov 23rd in 534 BC is the first documented instance of Acting. According to Aristotle it was an Icarian by the name of Thespis who first took on the character of others as an actor, instead of simply narrating their story. He used different masks for different characters, used different voices, and even had conversations with himself, acting the parts of multiple characters at the same time.
All of this was revolutionary at the time.
As an homage to the ‘father of tragedy’ we call those who tread the boards “thespians”.
The masks he used to portray characters have become a universal symbol for the theater. They also entered our vocabulary of self-examination. We will often speak of “wearing a mask” when we adopt a persona that may not be natural to us. Effectively we are “playing a part” much as an actor does. If my child fails an exam I may “adopt the mask” of the stern parent and give him a lecture on the need for study.
“All the world’s a stage”; from As You Like IT by William Shakespeare
All the world’s a stage,
And all the men and women merely players;
They have their exits and their entrances;
And one man in his time plays many parts,
His acts being seven ages. At first the infant,
Mewling and puking in the nurse’s arms;
And then the whining school-boy, with his satchel
And shining morning face, creeping like snail
Unwillingly to school. And then the lover,
Sighing like furnace, with a woeful ballad
Made to his mistress’ eyebrow. Then a soldier,
Full of strange oaths, and bearded like the pard,
Jealous in honour, sudden and quick in quarrel,
Seeking the bubble reputation
Even in the cannon’s mouth. And then the justice,
In fair round belly with good capon lin’d,
With eyes severe and beard of formal cut,
Full of wise saws and modern instances;
And so he plays his part. The sixth age shifts
Into the lean and slipper’d pantaloon,
With spectacles on nose and pouch on side;
His youthful hose, well sav’d, a world too wide
For his shrunk shank; and his big manly voice,
Turning again toward childish treble, pipes
And whistles in his sound. Last scene of all,
That ends this strange eventful history,
Is second childishness and mere oblivion;
Sans teeth, sans eyes, sans taste, sans everything.