Critic speak is tough, but we've got you covered.
Quote :Seven Types of Ambiguity
Most of the ambiguities I have considered here seem to me beautiful; I consider, then, that I have shown by example, in showing the nature of the ambiguity, the nature of the forces which are adequate to hold it together. It would seem very artificial to do it the other way round, and very tedious to do it both ways at once. I wish only, then, to say here that such vaguely imagined "forces" are essential to the totality of a poem, and that they cannot be discussed in terms of ambiguity, because they are complementary to it. But by discussing ambiguity, a great deal may be made clear about them. In particular, if there is contradiction, it must imply tension; the more prominent the contradiction, the greater the tension; in some way other than by the contradiction, the tension must be conveyed, and must be sustained.
Empson's 250-page book is basically a long list of literary ambiguities. But in this passage, he explains why he's interested in ambiguity. Ambiguity implies that something is open to multiple possible interpretations.
So, the existence of ambiguity implies the existence of contradictions. And if contradictions are afoot in a poem, then there's tension.
Stay with us now: poetry is a work of art that maintains the tension of ambiguity. Poems say a bunch of stuff without restricting their readers to any single interpretation of the text. Wow. Imagine doing that tightrope walk for the whole length of King Lear.
In any case, Empson was trying to point out that ambiguity's kinda at the heart of poetry—and of why poetry is beautiful.