Felt Change of Consciousness
The true source of the poetic, felt change of consciousness occurs when ordinary consciousness is "shed like an old garment" and one sees "in a new and strange light" (PD 48-49). This felt change is nothing less than the apprehension of meaning itself. The felt change of consciousness denotes "the momentary apprehension of the poetic by the rational, into which the former is forever transmuting itself--which it is itself for ever in process of becoming. . . . This is the very moonlight of our experience . . ." (PD 178). The felt change of consciousness is dependent upon the element of strangeness in poetry.

Barfield discovered the felt change of consciousness early on in his first encounters with poetry:

The way in which almost any intense experience of poetry reacted on my experience of the outer world [made a tremendous impression]. The face of nature, the objects of art, the events of history and human intercourse betrayed significances hitherto unknown as the result of precisely these poetic or imaginative combinations of words. . . . I found I knew (there was no other word for it) things about them which I had not known before. . . . those enhanced meanings may reveal hitherto unapprehended parts or aspects of reality. (RCA 10)
His B. Lit. thesis at Oxford, later published as Poetic Diction (1928), was inspired by these experiences. The idea of the felt change of consciousness lies at the heart of the thesis he expounds upon there.

To help explain this difficult-to-understand, quite ephemeral concept, Barfield uses an analogy drawn from electromagnetism:

It is not simply that the poet enables me to see with his eyes, and so to apprehend a larger and fuller world. He may indeed do this . . . , but the actual moment of the pleasure of appreciation depends on something rarer and more transitory. It depends on the change itself. If I pass a coil of wire between the poles of a magnet, I generate in it an electric current--but I only do so while the coil is positively moving across the lines of force.
    . . . Current only flows when I am actually bringing the coil in or taking it away again. So it is with the poetic mood, which, like the dreams to which it has so often been compared, is kindled by the passage from one plane of consciousness to another. It lives during the moment of transition and then dies, and if it is to be repeated, some means must be found of renewing the transition itself. (PD 52)
Certainly this should not surprise us, for we are well aware that the gestalt that makes poetry possible amounts to something like a law of experience generally. "We know instinctively that, if we are to feel pleasure, we must have change. Everlasting day can no more freshen the earth with dew than everlasting night, but the change from night to day and from day back again to night" (PD 53).

As gestalt psychology has taught us to see, we cannot experience both figure and ground at one and the same time. Nor can we live the wisdom which poetry give us--poetry's task being to add "extraordinary consciousness to our ordinary consciousness" (RM 30)--and experience its entrance into us simultaneously.

Inasmuch as man is living the poetry of which he is the maker, and as long as he is so doing, it cannot be poetry to him. In order to appreciate it, he himself must also exist, consciously, outside it; for otherwise the "felt change of consciousness" cannot come about. (PD 103)
Felt change of consciousness, then, marks the actual ontogenetic experience of evolution of consciousness, as Barfield explains in Poetic Diction's peroration, its closing words:
Over the perpetual evolution of human consciousness, which is stamping itself upon the transformation of language, the spirit of poetry hovers, for ever unable to alight. It is only when we are lifted above that transformation, so that we behold it as present movement, that our startled souls feel the little pat and the throbbing, feathery warmth, which tell us that she has perched. It is only when we have risen from beholding the creature into beholding creation that our mortality catches for a moment the music of the turning spheres. (PD 181)
See in particular Poetic Diction, passim; "Poetic Diction and Legal Fiction" (RM 44-64).