Full Idea
The design or intention of the author is neither available nor desirable as a standard for judging the success of a work of literary art.
Gist of Idea
The author's intentions are irrelevant to the judgement of a work's success
Source
W Wimsatt/W Beardsley (The Intentional Fallacy [1946], §I)
Book Reference
'Philosophy Looks at the Arts', ed/tr. Margolis,Joseph [Charles Scribner 1962], p.92
A Reaction
This famous proposal may have been misunderstood. Note that it is a comment about judging the work, not about understanding it. The idea allows for a work being much more successful than the author's humble intentions (e.g. Pepys).