Classic Poem

Are they shadows that we see?
And can shadows pleasures give?
Pleasures only shadows be,
Cast by bodies we conceive;
And are made the things we deem
In those figures which they seem.

But those pleasures vanish fast,
Which by shadows are exprest;
Pleasures are not, if they last;
In their passing is their best:
Glory is more bright and gay
In a flash, and so away.

Feed apace then, greedy eyes,
On the wonder you behold:
Take it sudden, as it flies,
Though you take it not to hold.
When your eyes have done their part
Thought must length'n it in the heart.