This slim volume is engaging and thought-provoking.  Michaelian discusses philosophical approaches to and theories of memory and builds a new theory which is compatible with the recent rapid growth of scientific knowledge of memory.  The result is heuristic.

          The author begins with a brief account of the philosophy of memory, with some emphasis on Locke, Hume and Reid, and points out that these venerable philosophical positions are incompatible with recent scientific findings.  He proposes to offer a new philosophical model.  The plan of the book is to provide a thorough description of episodic remembering in real people, a consideration of the reliability of episodic remembering, and ideas about the evolution of episodic memory.

          He provides an excellent, succinct account of major trends in research about memory, delineating between episodic memory, which is recall of past events, and semantic memory, which is recall of facts without recall of the episodes in which they were learned.  He points out that memory is often compared to new technologies (e.g. computers) and that this is a long-standing phenomenon:  Plato compared memory to writing on waxed tablets.

          Michaelian reviews contributions of Reid — “remembering involves internal representations of a real past event” — and Locke, for whom memory allows the mind “to revive perceptions, which it has once had, with this additional perception annexed to them, that it has had them before.”  He cites contributions from Russell and Quine.  Consistent with such approaches, Michaelian constructs an elegant model of a “causal theory” of memory, logically sound and comprehensive, only to discard it because it is not compatible with actual data on memory.

          What the data suggest, with converging evidence from many sources and types of research, is that remembering is imagining.  Van Leyden hinted at this with his comment that memories are more like paintings than photographs.  The same brain circuitry appears to be used for both memory and imagination.  Indeed, amnesic patients who cannot remember the past have trouble imagining futures.  Remembering appears to consist of imagining the past, which requires a sense of pastness.  (The author provides an excellent explication of the consciousness of subjective time — chronesthesia — in the book.)

          So memory is not exclusively about the past.  And remembering is really not a matter of reproducing but of recreating an episode.  Michaelian concludes that episodic memory is a form of “mental time travel”, a term which has also been used in memory research.  Remembering — and the science bears this out — is not the reproduction of an episode but its re-creation.

          Michaelian rejects his causal theory in favor of a simulation theory, which is elegant, consistent with evidence, and counter-intuitive.  But it seems to work.  It is essential to test whether such a model provides accurate representations, and it appears to do so frequently.

          A question about this theory is whether it will be overrun by “false memories”.  If memory is imagination, will it inevitably be unreliable?  Most clinical experience of false memories came from the epidemic of multiple personality disorder (by its then current name) in the 1980’s, which was a hysterical phenomenon.  But Michaelian constructs a different type of false memory, an example of which is a lecturer who has no memory of a lecture he gave.  But because of having given several lectures on the same topic, knowing the students in the class, the lecturer’s opinions on the subject, familiarity with the lecture hall, etc., the lecturer can generate a detailed image of the lecture he cannot recall.  He remembers the lecture even though he does not.  This type of “false memory” may not be false, but “harmful incorporation” can occur, leading to false memories.  But the data support most episodic memory being reasonably accurate, but, as Von Leyden wrote, “The missing pieces of an episode may be filled in by information from other sources.”

          The author addresses the subjectivity of the sense of memory, which relies on consciousness of the self, autonoetic consciousness.  He quotes Merleau-Ponty, that our sense of pastness “is not contained in or directly determined by retrieved information.”  Many philosophers adopt a doctrine of “privileged access” — the assumption that our knowledge of the mental states of others is inferiential and accordingly fallible in ways that our knowledge of ourselves is not.  But this is axiomatic and not conducive to proof.  Wittgenstein criticized the concept as being an artefact of rules of language.  But, while our self-knowledge of pastness and memory is an appealing part of the theory, it is not essential to it.

          The comments on the evolution of memory are interesting, highly speculative, and, to me, neither compelling nor essential to the book.

          Michaelian’s goals for the book were to provide an account of episodic remembering and its reliability, with comments about its evolution.  He provides a carefully constructed simulation theory of memory which is consistent with scientific data to date.  The details of this theory will surely be replaced as more work is done, but, as he states, “The point of the book is that, ultimately, it doesn’t matter.”

          This is a wonderful, short book.  The author makes a compelling case that memory is imagining.  He succinctly summarizes and explains a plethora of studies.  The writing is simple, comprehensible, and sometimes funny.

          My negative comments are trivial.  I wish that Michalian had discussed more philosophers who contributed to theories of memory — Rousseau and Berkeley are notably absent,  as is Descartes, who made fundamental contributions.   And in discussing episodic memory, the author generally treats it as a natural kind, even though he quotes Patricia Churchland indicating that we do not know “whether memory is a natural kind or, instead, a set of disparate phenomena only superficially similar to one another.”

          To me, what is most exciting about this book is its demonstration that good philosophy and good science are not incompatible, that philosophy can inform science — and Michaelian’s simulation theory could be paradigmatic in the continued development of the science of memory — and that science can inform philosophy.

          The notes, references and index are helpful and very well done.

          Some years before Michaelian’s book, St. Augustine wrote, “Out of the same storehouse, with these past impressions, I can construct now this, now that, image of things that I either have experienced or have believed on the basis of experience — and from these I can further construct future actions, events and hopes; and I can meditate on all these things as if they were present.”

 

© 2016 Lloyd A. Wells

 

Lloyd A. Wells is a retired psychiatry consultant at Mayo Clinic.