"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 honor, 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 lined, 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 saved, 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."
The line "all the world's a stage" is one of the most quoted of Shakespeare. The "stage" referenced has nuanced meanings. First, there are the literal stages of life, from infancy to death. Then, there is the metaphor that mankind is merely performing a predetermined role as part of a grander production. Our roles, Shakespeare seems to be writing, are largely not of our own making. Mankind follows a similar path, and no matter how we act our parts -- our lives -- we all end up the same: in "mere oblivion." The speech is a dark moment is what otherwise is considered a comedic play, and contrasts the optimism of other characters with the defeatist, dour Jaques.