T. S. Eliot praises Donne's ability to unify the intellectual thought and sensation of feeling. Why?
T. S. Eliot's "dissociation of sensiblity" states that intellectual thought was seperated from feeling; however, his statement about Donne is CONTRARY. Why?
I haven't read T.S. Eliot's essay "The Metaphysical Poets" (1921) in quite a long time and had to review it briefly to make sure I wasn't completely off base, but I recall Eliot's argument to be that Donne's poetry reflects how things were for the poet before the supposed "dissociation of sensibility" set in.
Eliot explicitly contrasts Donne to later, Victorian-era poets: "Tennyson and Browning are poets, and they think; but they do not feel their thought as immediately as the odour of a rose. A thought to Donne was an experience; it modified his sensibility." He goes in the next paragraph to develop what he calls the "theory" of "a dissociation of sensibility":
We may express the difference by the following theory: The poets of the seventeenth century, the successors of the dramatists of the sixteenth, possessed a mechanism of sensibility which could devour any kind of experience. They are simple, artificial, difficult, or fantastic, as their predecessors were; no less nor more than Dante, Guido Cavalcanti, Guinicelli, or Cino. In the seventeenth century a dissociation of sensibility set in, from which we have never recovered; and this dissociation, as is natural, was aggravated by the influence of the two most powerful poets of the century, Milton and Dryden. Each of these men performed certain poetic functions so magnificently well that the magnitude of the effect concealed the absence of others. The language went on and in some respects improved; the best verse of Collins, Gray, Johnson, and even Goldsmith satisfies some of our fastidious demands better than that of Donne or Marvell or King. But while the language became more refined, the feeling became more crude. The feeling, the sensibility, expressed in the Country Churchyard (to say nothing of Tennyson and Browning) is cruder than that in theCoy Mistress.
So, to answer your question (I hope), Eliot praises Donne and the metaphysical poets in general and finds a deficit, if we can call it that, in the more modern poets. I've always understood Eliot to be talking here more about himself and his modernist contemporaries than he is about Victorian poetry.
Once again, this is just to add to the strong answer already posted. Eliot's masterful essay "Tradition and The Individual Talent" may be another vantage-point from which this praise of Donne's unification of emotion and intellect can be analyzed.
We can relate this praise to Eliot's general theory of poetry not as an expression of emotion but rather as an escape from emotion. In the aforementioned essay, he stressed the all important gap between the experiencing self and the creative self as an internal division within the poet. The retention of this distance between the two is crucial for the creation of great poetry. While this take is often seen as merely anti-Romantic and thus anti-emotional, I do not think that Eliot was trying to banish emotion from the world of poetry but instead he was trying to redefine poetic emotion as an intellectualized construct, also related to the poet's evocation of his medium.