| This is the original form of the famous aphorism. The entire passage, from Part 3 of Alexander Pope's An Essay on Criticism goes:
Such shameless Bards we have; and yet 'tis true,
There are as mad, abandon'd Criticks too.
The Bookful Blockhead, ignorantly read,
With Loads of Learned Lumber in his Head,
With his own Tongue still edifies his Ears,
And always List'ning to Himself appears.
All Books he reads, and all he reads assails,
From Dryden's Fables down to Durfey's Tales.
With him, most Authors steal their Works, or buy;
Garth did not write his own Dispensary.
Name a new Play, and he's the Poet's Friend,
Nay show'd his Faults--but when wou'd Poets mend?
No Place so Sacred from such Fops is barr'd,
Nor is Paul's Church more safe than Paul's Church-yard:
Nay, fly to Altars; there they'll talk you dead;
For Fools rush in where Angels fear to tread.
Distrustful Sense with modest Caution speaks;
It still looks home, and short Excursions makes;
But ratling Nonsense in full Vollies breaks;
And never shock'd, and never turn'd aside,
Bursts out, resistless, with a thundering Tyde!
A pious freethinker and a dense writer, Pope was probably not innocent of the overtones of criticism of the church; watch the subtle play over "learned ignorance" - someone who'se memorized vast texts (i.e. the Bible) rather than learned to understand them - to plagiarism - to the preacher, "Nay, fly to altars..." Are Pope's priests critics of God?
Another, far less inflammatory, explanation follows from four lines elided following the cliche:
In vain you shrug, and sweat, and strive to fly;
These know no manners but in poetry.
They'll stop a hungry chaplain in his grace,
To treat the unities of time and place.
These lines would make the chaplains victims of criticism together with the poets. It's interesting, in any case, to consider why they might have been removed. | 
