The most radical aspect of Owen Barfield's metaphysical thinking, which he shares with (and probably got from) Rudolf Steiner, is that all knowledge entails consciousness.
Reality is partly-produced-by consciousness; because everything we know or might know involves us knowing it, which entails consciousness part-creating everything.
Or, there is nothing we know of, in which consciousness does not have some role: we are never able actually to separate consciousness from the 'outer' world of 'objective' phenomena and access any supposed objective-reality independent of consciousness.
Consciousness participates in reality.
Negatively, this means that many of our normal, everyday ways of thinking are invalid and necessarily untrue; because they model 'reality' without our own participating consciousness. In other words, all of normal science is necessarily untrue - and actually, merely therefore, rules-of-thumb that seem to work at present and in the conditions we have used them... because they exclude the participating consciousness.
This is a really deep-cutting idea. I first came across it in Worlds Apart - which is Barfield's somewhat Inklings-like Platonic dialogue published in 1963 (and re-read by CS Lewis multiple times in the last few months of his life). I was confused and brought-up short by the relevant passages; I could hardly believe that Barfield was serious, and thought I must have misunderstood.
But I have gradually come to feel compelled to share this basic metaphysical assumption. Because it is a metaphysical assumption - however it is probably not genuinely weird, and instead probably the most natural and spontaneous human assumption we make about reality.
We begin life assuming that everything in the world relates to us and our knowledge of it; but by adulthood this attitude has become regarded as a 'paranoid delusion of self-reference'; and we assume that all true descriptions of reality leave-out the human - including leaving-out the observing/ participating consciousness.
Barfield's example is the evolution of the earth and biological-life upon it - typically, modern science regards this as autonomous of human consciousness, and indeed the story has to explain how human consciousness arose towards the end of the planetary period under consideration. But the Barfield/ Steiner metaphysics refuses to talk about a time or place when there was no consciousness, because this is metaphysical nonsense - instead there is a focus on how consciousness has changed (for example, changing from something diffuse and interpenetrating, to something focused and discrete).
What is actually spontaneous and built-in to Men has now become extremely difficult and strange for modern Man: thinking in a way that is coherent with the fact of Man's own thinking has become unnatural to us. Even in theology, it is normal to discuss God without any reference to Man's participating consciousness - yet everything we think or say or write about God involves Man's consciousness.
I could not say I have done more than very partially assimilate the profundity of such a change in metaphysical perspective - the rationale for which was sketched out by Coleridge, Steiner (especially in his earliest and purely philosophical books) and Barfield; but it is just something very hard to grasp and believe for a Modern Man (perhaps especially for an evolutionary scientist such as myself?).
But it is something which I think must be correct. Which means that almost all of our current ways of thinking and reasoning, almost all that we think we know, is necessarily wrong, misleadng, error-generating --- And so I need to continue to develop new habits of thinking in-line with the participation of consciousness, which would enable me to work-from this metaphysical assumption in as many ways as possible.