The physical background for the quantum-mechanical ideas presented in Morowitz’s article and the accompanying Reflection is available at several levels of difficulty. A stimulating elementary presentation is that by Adolph Baker in Modern Physics and Anti-physics (Reading, Mass.: Addison-Wesley, 1970). And there is Richard Feynman’s The Character of Physical Law (Cambridge, Mass.: MIT Press, 1967). At an intermediate level, using a bit of mathematics, are J. Jauch’s elegant dialogues Are Quanta Real? (Bloomington: Indiana University Press, 1973) and The Feynman Lectures in Physics, vol. III, by Richard Feynman, Robert Leighton, and Matthew Sands (Reading, Mass.: Addison-Wesley, 1963). An advanced treatise is the monograph The Conceptual Development of Quantum Mechanics by Max Jammer (New York: McGraw-Hill, 1966). There is also a further-out book, edited by Ted Bastin, called Quantum Theory and Beyond: Essays and Discussions Arising from a Colloquium (Cambridge, Eng.: Cambridge Univ. Press, 1971) containing many speculative selections. Eugene Wigner, one of the major figures in physics this century, has devoted an entire selection, in his book of essays entitled Symmetries and Reflections (Cambridge, Mass.: MIT press, 1970), to the subject of “Epistemology and Quantum Mechanics.”
Hugh Everett’s original paper is found, together with discussions by other physicists, in The Many-Worlds Interpretation of Quantum Mechanics (Princeton, N.J.: Princeton University Press, 1973), edited by B.S. Dewitt and N. Graham. A recent and much easier book on these puzzling splitting worlds is Paul Davies’ Other Worlds (New York: Simon & Schuster, 1981).
The strange problem of personal identity under such conditions of branching has been explored, indirectly, in a high-powered but lively debate among philosophers over the claims made by the philosopher and logician Saul Kripke in his classic monograph “Naming and Necessity,” which first appeared in 1972 in D. Davidson and G. Harman, eds., The Semantics of Natural Language (Hingham, Mass.: Reidel, 1972), and has just been reprinted, with additional material, as a book by Kripke, Naming and Necessity (Cambridge, Mass.: Harvard University Press, 1980). In the Reflections, an issue is raised that must have occurred to you before: If my parents hadn’t met, I’d never have existed—or could I have been the child of some other parents? Kripke argues (with surprising persuasiveness) that although someone exactly like you might have been born at a different time to different parents—or even to your own parents—that person could not have been you. Where, when, and to whom you were born is part of your essence. Douglas Hofstadter, Gray Clossman, and Marsha Meredith explore this strange terrain in “Shakespeare’s Plays Weren’t Written by Him, but by Someone Else of the Same Name” (Indiana University Computer Science Dept. Technical Report 96) and Daniel Dennett casts some doubt on the enterprise in “Beyond Belief,” forthcoming in Andrew Woodfield, ed., Thought and Object (New York: Oxford University Press, 1981). Meaning, Reference and Necessity (New York: Cambridge University Press, 1975), edited by Simon Blackburn, is a good anthology of work on the issue, and the topic continues to be analyzed in current and forthcoming articles in major philosophy journals.
Morowitz cites recent speculation about the sudden emergence of a special sort of self-consciousness in evolution—a discontinuity in the development of our remote ancestors. Certainly the boldest and most ingeniously argued case for such a development is Julian Jaynes’s The Origins of Consciousness in the Breakdown of the Bicameral Mind (Boston: Houghton Mifflin, 1976), in which he argues that consciousness of the familiar, typically human sort is a very recent phenomenon, whose onset is datable in historical times, not biological eons. The human beings told of in Homer’s Iliad, Jaynes insists, were not conscious! That is not to say they were asleep, or unperceiving, of course, but that they had nothing like what we think of as our inner lives. Even if Jaynes has overstated his case (as most commentators think), he has posed fascinating questions and drawn attention to important facts and problems hitherto unconsidered by thinkers on these topics. Incidently, Friedrich Nietzsche expressed a similar view of the relation of consciousness and social and linguistic practices in Die fröhliche Wissenschaft (1882), translated by Walter Kaufmann as The Gay Science (New York: Random House, 1974).
The Turing test has been the focus of many articles in philosophy and artificial intelligence. A good recent discussion of the problems it raises is “Psychologism and Behaviorism” by Ned Block, in The Philosophical Review (January 1981, pp. 5–43). Joseph Weizenbaum’s famous ELIZA program, which simulates a psychotherapist with whom one can hold an intimate and therapeutic conversation (typing on a computer terminal), is often discussed as the most dramatic real-life example of a computer “passing” the Turing test. Weizenbaum himself is appalled by the idea, and in Computer Power and Human Reason (San Francisco: Freeman, 1976), he offers trenchant criticism of those who—in his opinion—misuse the Turing test. Kenneth M. Colby’s program PARRY, the simulation of a paranoid patient that “passed” two versions of the Turing test, is described in his “Simulation of Belief Systems,” in Roger C. Schank and Kenneth M. Colby, eds., Computer Models of Thought and Language (San Francisco: Freeman, 1973). The first test, which involved showing transcripts of PARRY’s conversations to experts, was amusingly attacked by Weizenbaum in a letter published in the Communications of the Association for Computing Machinery (vol. 17, no. 9, September 1974, p. 543). Weizenbaum claimed that by Colby’s reasoning, any electric typewriter is a good scientific model of infantile autism: type in a question and it just sits there and hums. No experts on autism could tell transcripts of genuine attempts to communicate with autistic children from such futile typing exercises! The second Turing test experiment responded to that criticism, and is reported in J. F. Heiser, K.M. Colby, W.S. Faught, and K.C. Parkinson, “Can Psychiatrists Distinguish a Computer Simulation of Paranoia from the Real Thing?” in the Journal of Psychiatric Research (vol. 15, 1980, pp. 149–62).
Turing’s “Mathematical Objection” has produced a flurry of literature on the relation between metamathematical limitative theorems and the possibility of mechanical minds. For the appropriate background in logic, see Howard De Long’s A Profile of Mathematical Logic (Reading, Mass.: Addison-Wesley, 1970). For an expansion of Turing’s objection, see J. R. Lucas’s notorious article “Minds, Machines, and Gödel,” reprinted in the stimulating collection Minds and Machines, edited by Alan Ross Anderson (Engelwood Cliffs, N.J.: Prentice-Hall, 1964). De Long’s excellent annotated bibliography provides pointers to the furor created by Lucas’s paper. See also Gödel, Escher, Bach: an Eternal Golden Braid by Douglas R. Hofstadter (New York: Basic Books, 1979) and Mechanism, Mentalism, and Metamathematics by Judson Webb (Hingham, Mass.: D. Reidel, 1980).