I've heard theories that time is not necessarily linear ...
René Guénon, in "The Multiple States of the Being" offers:
"... consciousness in the individual human state, like this state itself, is nonetheless capable of indefinite extension; and even in the ordinary man, that is, one who has not especially developed his extra-corporeal modalities, it in fact extends much further than is commonly supposed.
"... but if the psychologists readily recognize the existence of a 'subconscious' ... they always forget to envisage correlatively a 'superconscious' ...
"... in reality both the 'subconscious' and the 'superconscious' are simple prolongations of consciousness itself and can never take us out of its integral domain, and consequently cannot in any way be compared to the 'unconscious', that is, to what is outside of consciousness, but on the contrary must be included in the complete notion of the individual consciousness.
"Considered in this way, the individual consciousness suffices to account for everything that takes place mentally in the domain of individuality, without need for recourse to the bizarre hypothesis of a 'plurality of consciousnesses', which some people have even understood in the sense of a literal 'polypsychism'. It is true that the 'unity of the self', as ordinarily envisaged, is equally illusory, but if this is so, it is precisely because plurality and complexity exist in the very heart of the consciousness, which prolongs itself in modalities some of which may be very distant and obscure, such as those that constitute what might be called 'organic consciousness', as well as most of those manifested in the dream state.
"From another point of view the indefinite extension of consciousness renders completely useless certain strange theories that have surfaced in our time, of which the metaphysical impossibility suffices to refute completely. Here we do not intend to speak only of the more or less 'reincarnationist' hypotheses, and others comparable to them, as implying a similar limitation of Universal Possibility ..."
(
The Multiple States of Being, Chapter 7: "The Possibilities of Individual Consciousness", Sophia Perennis, New York, 2004, p.43-44)
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Guénon was somewhat adamant that rebirth as a human being was a one-time event, as the idea of someone (and who, or rather what, is never adequately defined) coming back time and again, in Guénon's metaphysic, was a no-no. Furthermore, Guénon argued the popular theory of reincarnation was a largely western idea and not taught in the authentic traditions.
Marco Pallis offered, to the contrary, that:
"... he (Guénon) wished rather to emphasize the principial simultaneity of that which, from the standpoint of ordinary experience, appears as successive: the "guénonian" presentation of the
Multiple States of the Being is a static version of the same truth which
samsara traditionally expresses in dynamic mode... whence his statement that, among Hindus, their frequent references to rebirth in human form are consciously intended to be read in a symbolical sense only, and that it is Western misunderstanding, notably on the part of Theosophists, that is exclusively responsible for current reincarnationist phraseology. Having had much to do with both Brahmins and Lamas in their own countries I can only say that as a statement of fact the above mentioned view does not hold water.
While I feel sure that all are agreed in rejecting the possibility of
repetition in the arising and existence of beings, as spelling metaphysical nonsense, the possibility of another (but different) human birth is not formally ruled out by the Orientals; for them, this possibility goes in with the rest of
samsara and they neither try to limit it in positive or negative terms. One can perhaps best express the traditional view by saying that human birth is a rare and correspondingly precious opportunity, determined like everything else in an indefinite Round of Existence by antecedent
karma. Popular simplifications apart, this is the doctrine one meets in Asia."
(Letter entitled 'Reincarnation' in
Studies in Comparative Religion, Vol.1, No.1)