i've rather neglected martin buber in my philosophical wanderings, though on a number of occasions people who have heard my schtick (esp with regard to metaphysics or ontology) have been all like, "you better go read buber". at any rate, in this rather stunning bit from the third part of i and thou, i recognize my sort of position:
All doctrines of immersion are based on the gigantic delusion of a human spirit bent back on itself - the delusion that spirit occurs in man. In truth it occurs from man - between man and what he is not.
the context is a discussion of the teachings of the buddha, and 'doctrines of immersion' are doctrines according to which we have to more or less annihilate ourselves to achieve an identity with things, or with the world, or with god. buber thinks such views actually presuppose a human spirit trapped in itself, and no human spirit is trapped in itself; it is always in transaction, or it is a series of transactions. for philosophy-heads: this also appears to be an expression of externalism about the mind, or at rate the spirit (whatever that may be, exactly; anyway, it's not much more mysterious than mind).