"Why Should Not Old Men Be Mad?" by Yeats

Why should not old men be mad?
Some have known a likely lad
That had a sound fly-fisher's wrist
Turn to a drunken journalist;
A girl that knew all Dante once
Live to bear children to a dunce;
A Helen of social welfare dream,
Climb on a wagonette to scream.
Some think it a matter of course that chance
Should starve good men and bad advance,
That if their neighbours figured plain,
As though upon a lighted screen,
No single story would they find
Of an unbroken happy mind,
A finish worthy of the start.
Young men know nothing of this sort,
Observant old men know it well;
And when they know what old books tell
And that no better can be had,
Know why an old man should be mad.