A remarkable hypothesis has recently been advanced by Libet and promoted by Eccles which claims that there is standardly a backwards referral of conscious experiences in time, and that this constitutes empirical evidence for the failure of identity of brain states and mental states. Libet's neurophysiological data are critically examined and are found insufficient to support the hypothesis. Additionally, it is argued that even if there is a temporal displacement phenomenon to be explained, a neurophysiological explanation is most likely.

Voluntary acts are preceded by electrophysiological (RPs). With spontaneous acts involving no preplanning, the main negative RP shift begins at about200 ms. Control experiments, in which a skin stimulus was timed (S), helped evaluate each subject's error in reporting the clock times for awareness of any perceived event.

Evidence that led to the hypothesis of a backwards referral of conscious sensory experiences in time, and the experimental tests of its predictions, is summarized. Criticisms of the data and the conclusion by Churchland that this hypothesis is untenable are analysed and found to be based upon misconceptions and faulty evaluations of facts and theory. Subjective referral in time violates no neurophysiological principles or data and is compatible with the theory of "mental" and "physical" correspondence.

Sensation elicited by a skin stimulus was subjectively reported to feel stronger when followed by a stimulus to somatosensory cerebral cortex , even when C was delayed by up to 400 ms or more. This expands the potentiality for retroactive effects beyond that previously known as backward masking. It also demonstrates that the content of a sensory experience can be altered by another cerebral input introduced after the sensory signal arrives at the cortex. The long effective S-C intervals support the (...) thesis that a duration of cortical activity of up to 0.5 s is required before awareness of a sensory stimulus is developed. (shrink)

The prima facie heterogeneity between psychical and physical phenomena seems to be a serious objection to psychoneural identity thesis, according to many authors, from Leibniz to Popper. It is argued that this objection can be superseded by a different conception of consciousness. Consciousness, while being conscious of something, is always unconscious of itself . Consciousness of being conscious is not immediate, it involves another, second-order, conscious state. The appearance of mental states to second-order consciousness does not reveal their true nature. (...) Psychoneural identity can thus be considered a valid hypothesis. Related views of Kant, Freud, Shaffer, Bunge and others are considered. “Naive psychical realism” is criticised. Consciousness of mental events is considered as the result of the action of a cerebral system that observes the neural events hypothetically identical to mental events. The theory combines a materialist view with a due consideration of subjective experience. (shrink)