Owen Barfield's central idea, and the one for which he is best known, is the evolution of consciousness - meaning that the nature of human consciousness has changed throughout history such that people in different eras and places had very different relationships with the world: these changes fall into three general categories of Original Participation, the Observing Consciousness and Final Participation.
He traces the evolution of consciousness mainly by observing the characteristic changes in the meaning and usage of words, which seem to display a cohesive development - and also looks at other cultural evidence. Barfield's idea of evolution in this regard is not natural selection, but a developmental process (akin to the growth and differentiation of a living entity): the emergence and unfolding of human destiny, interacting with the agency and free will of individual humans.
What is seldom appreciated or emphasized is that for Barfield the evolution of consciousness is divinely designed, and bound-up with reincarnation. To put it concisely, the reason for the evolution of consciousness through history is that this provides the necessary conditions by which successive reincarnations of human spirits may learn what they require to develop towards divinity.
So, for Barfield (although this is hinted at much more often than made explicit) it is God who 'provides' the evolution of consciousness in order that reincarnating human spirits may have the necessary experiences they need to growth towards the ultimate goal of Final Participation - whereby firstly, and stepwise, the Ego or Self has become separated from its original 'unconscious' immersion in the environment and strong in its purpose and will - awake, alert and in-control; then secondly the now strong and purposive Self/ Ego comes back into a participatory relationship with The World.
To underlying rationale (the 'point') of the evolution of consciousness is, for Barfield, bound-up with the reality of reincarnation; and therefore those (such as myself) who disbelieve in reincarnation as the normal human destiny, yet who believe in the evolution of consciousness, need to be clear that we differ from Barfield; and are, indeed, denying the main reason for evolution of consciousness as Barfield understood it.
To put it bluntly: those individuals who are sympathetic towards Barfield's core idea of the evolution of consciousness yet who do not believe in reincarnation, need to explain what the evolution of consciousness is for - if not to provide the conditions necessary for educating the reincarnating human spirit.
Note: My personal 'take' on reincarnation is that it is not the normal human destiny - but that reincarnation happens to some individuals for particular purposes - for instance, a sage, prophet or saint may be a reincarnate who has returned to assist in the divine work - indeed I suspect that many of the wise intuitive individuals such as Rudolf Steiner and perhaps Owen Barfield himself, who claim direct personal knowledge of the reality of incarnation, are themselves actually some of these rare and atypical persons. As a believer in Mormon theology, my explanation for the evolution of consciousness is that humans have a pre-mortal spiritual existence before being voluntarily incarnated into life on earth - and the evolution of consciousness allows pre-mortal spirits to be 'placed' - by God - into the historical era which best addresses their personal spiritual needs: i.e. their specific needs for mortal experience of a particular kind.