The Tides of David Gelernter's Mind

A dazzling new book reminds us that our minds don’t work like computers—and that wisdom, including the moral wisdom of Judaism, doesn’t progress like science.

Sept. 1 2016
About the author

Moshe Koppel is a member of the department of computer science at Bar-Ilan University and chairman of the Kohelet Policy Forum in Jerusalem.

I’m sitting on the couch deliberating hard about how best to tie together the various strands of David Gelernter’s dazzling new book, The Tides of Mind. Drifting off into a reverie, I re-experience reading the book while sitting on the beach in Tel Aviv. Then I become aware that I’ve drifted off and, inspired by the book, begin to reflect on the experiential qualities of the daydream, only to realize that I can’t have my daydream and reflect on it at the same time.

What is it like to think deliberately about some problem that we wish to solve? What is it like to daydream? How are these experiences similar to or different from the experience of actual dreaming? Since we have such experiences all the time, we ought to know everything there is to know about them. And yet, precisely because of the difficulty of both having experiences and reflecting on them, we are surprisingly oblivious of the patterns underlying the dynamics of our mental states.

The Tides of Mind seeks to remedy this deficit. Its author is a Yale professor of computer science whose writings for non-specialist readers include such luminous works as Mirror Worlds (1992) and The Muse in the Machine (1994). In addition, Gelernter paints, writes fiction, and has built a reputation as an acute social and cultural critic through essays in Commentary, the Weekly Standard, the Wall Street Journal, and elsewhere. A committed Jew—as an undergraduate at Yale, he majored in Bible and classical Hebrew literature—he is also the author of Judaism: A Way of Being (2009), a book, and a subject, to which we’ll return in due course.


In The Tides of Mind, Gelernter draws on his own introspective thoughts to line up our familiar mental states—active thinking, daydreaming, transition to sleep, dreaming—along a single dimension that he calls the “spectrum of consciousness.” In doing so, he triangulates his thoughts with those of a gallery of great writers, among whom he is especially fond of Jane Austen, Marcel Proust, J.M. Coetzee, Cynthia Ozick, and the English Romantic poets. Let’s follow along.

As we move through a typical day, Gelernter writes, the varying states of our consciousness are characterized by a number of correlated parameters. At the “high end” of the spectrum, we’re thinking, necessarily about something; at the “low end,” we’re just feeling. At the high end, we consciously draw on memory as needed; at the low end, memories wash over us and we re-experience them. At the high end, we organize our thoughts using logic; at the low end, our memories organize themselves into narratives. At the high end, we communicate our thoughts voluntarily, through language; at lower ends, we communicate our feelings involuntarily, via facial expressions, gestures, tone of voice, and the like.

Crucially, the high end and the low end sit on a continuum. In a typical day, we alternately ascend and descend the spectrum, pulling slowly out of the external world and into our minds, and back again, as we gradually traverse the spectrum from active thinking to daydreaming to the onset of sleep to dreaming to unconsciousness. Gelernter carefully notes the patterns according to which this journey transpires during the course of the day, in a manner akin to the daily rise and fall of sea levels: hence, the “tides” of mind.

Gelernter is aware that universalizing on the basis of his own introspection is a dangerous proposition— like Truman Burbank in The Truman Show, he might just be circling inside the stage set of his own mind. But he correctly stipulates that his introspective claims can and should be judged on the basis of their resonance with the reader.

They resonated with this reader.


But that is not all there is to this book. More is going on than a painstaking description of the spectrum of consciousness, though that is surely a worthy achievement in its own right. Implicitly, Gelernter is leveling a critical judgment against contemporary scientific researchers—and ultimately against all of modern society—for valuing the high end of the spectrum at the expense of the lower ones. As he puts it, “[T]he middle- and lower-spectrum thirds put modern thinkers on edge. They are a bad match to our science-venerating climate.”

One of his purposes is therefore to refocus our “science-venerating” attention onto the lower levels of the spectrum. It is there where, in Gelernter’s view, deeper knowledge —concerning human nature, the purposes of our lives, the distinction between right and wrong—is revealed to us. We can’t reason our way to such knowledge; we must feel it.

Unlike up-spectrum scientific thought, which is cumulative and progressive, down-spectrum knowledge is born anew in each mind and is often diminished over time. Children, Gelernter observes, prior to developing the tools of logic and language, do not reach the upper end of the spectrum at all. Their world is unreflective, dominated by emotions and, because unpredictable by them, seemingly magical; their world is vivid to them, something akin to a dream. Gelernter cites the opening stanza of William Wordsworth’s Ode, Intimations of Immortality:

There was a time when meadow, grove, and stream,
The earth, and every common sight,
To me did seem
Apparell’d in celestial light,
The glory and the freshness of a dream.
It is not now as it hath been of yore;—
Turn wheresoe’er I may,
By night or day,
The things which I have seen I now can see no more.

As we mature and shift much of our waking lives up-spectrum, we pay a price: we lose sight of the “celestial light.”

Can we ever retrieve it? In this connection, disclosing his interest in religious experience, Gelernter offers a tantalizing hint at the mechanics of spirituality. Down-spectrum, he writes, where emotions sometimes wash over us, otherwise disparate concepts can evoke a similar emotion and thereby become linked. From this perspective, the spiritual experience of the “oneness of the universe” can be seen as a form of emotion-driven “surfing” along the space of such linked concepts: a rare gift of celestial light.

More commonly, what is true for individuals is true historically for societies as well. In ancient times, “people lived lower on the spectrum,” and “spiritually-minded people were more common” than now. The Bible, whose “native landscape” is the “visual, subjective reality of the lower spectrum,” speaks of and to such people. But as our cultures move up-spectrum, focusing increasingly on conscious rational thought, we become less emotionally attuned, and the Bible’s prophetic messages are attenuated. Just as children outgrow the ability to see the celestial light with the freshness of a dream, so moderns, in Gelernter’s telling, have lost not only the ability to experience prophecy but even, to a great extent, the ability to understand the prophetic biblical messages in which dream and reality intermingle.


David Gelernter is a prominent computer scientist. But, as I’ve already suggested, he is wary of the limitations of science—its difficulty in capturing inherently subjective phenomena using scientific tools—and also of the excesses of scientists: specifically, their failure to acknowledge the limitations of those tools. This may be one reason why in The Tides of Mind he almost never cites the hard sciences, relying instead on poets and novelists, and pouring on the quotations.

This leads, however, to some disturbing omissions. A reader might come away from the book thinking—wrongly—that scientists themselves have nothing useful to say about either the higher or the lower levels of the spectrum of consciousness.

It is certainly true that scientists are tempted to focus greater attention on the higher levels, and on the mechanics of deliberate thought. That is at least understandable: reflective thought is more accessible to, well, reflection. It is also uniquely susceptible of analysis by means of science’s best contemporary trick: simulation by means of computational tools. And this in turn has nourished the now-popular but problematic doctrine that computational models of the mind are fully equivalent to the mind itself.

Many writers—including John Searle, Thomas Nagel, and Gelernter himself—have pointed out that this equivalence is rooted in a category error: objective function is not the same as subjective experience. Nevertheless, the technological evidence accumulating in the fields of artificial intelligence and robotics is intrinsically compelling. In recent years, deep neural nets—a method, loosely based on the structure of the brain, by which computers learn to generalize from examples—have made astonishing strides in the recognition and processing of both texts and images, exceeding human competence at a wide variety of tasks. No one can predict where this and other such initiatives will lead (which of course has not stopped anyone from predicting); but that is no reason for ignoring them.

Similarly, one may grant that a phenomenological description of the experience of mental states, especially at the lower levels of the spectrum, is generally better served by insightful writers than by science geeks. But the distinction between low-spectrum instincts and emotions and high-spectrum conscious thought—the distinction so central to Gelernter’s argument—has hardly gone unnoticed by scientists.

Our everyday judgments—social, economic, moral—plainly draw both on deliberate reasoning and on unconscious instincts. How do these two modes differ? How do they interact? Why did universal human instincts and emotions evolve in the particular way they did? How are they encoded in the brain? These are some of the most widely researched and hotly debated questions in contemporary science and in a variety of related disciplines, including behavioral economics, moral psychology, neuroanatomy, and cultural evolution. They bear directly on some of the questions that Gelernter is dealing with. It is a pity that he neglects to take note of this copious literature—and to contend with it.


Gelernter has a long track record of writing both on cultural issues and on matters of Jewish concern; he does so from a politically and religiously conservative perspective. While The Tides of Mind is not an overtly political or religious work, it is of a piece with concerns expressed elsewhere by Gelernter, especially in Judaism: A Way of Being.

The common theme, as I noted earlier, is the low-spectrum character of classical Judaism, particularly in its biblical roots, and the gradual diminishment of the ability properly to comprehend the prophetic message (the “decline of the generations”). Indeed, just as in The Tides of Mind, so in Judaism before it, Wordsworth’s Intimations appears toward the climax of the argument.

Here one might raise a qualification in the form of an addendum. The whole point of Judaism is to preserve, even in the absence of prophetic aptitude, the moral essence of the prophetic message—a task it accomplishes through specific legal traditions. It may be helpful to consider how this process works on both the individual and the societal level.

In its general outline, the process is hardly unique to Judaism. By the time we are two years old, we know viscerally—low-spectrum—that it is wrong to hit our friends or take their toys; after just a bit of socialization, we also know viscerally that incest is wrong and that ridiculing our parents is wrong. But moral feelings, visceral as they may be, are often vague, especially when they must compete with conflicting selfish feelings. Thus, societies evolve traditions meant to capture, at least in part, some aggregate moral sense. These traditions, especially when codified, then serve as a proxy for our internal moral sense; that is, we make moral decisions by following tradition rather than by following our instincts.

In Judaism in particular, the process of determining what tradition demands in a given new instance involves high-spectrum analysis of the existing corpus of traditional thought and religious legislation. Thus, committed Jews face a subtle tradeoff. On the one hand, it is only by carefully codifying and incrementally refining tradition that they preserve moral values even under conditions of instability, upheaval, and no-longer-audible moral instincts. On the other hand, they run the risk of confusing the proxy for the real thing: allowing the technical details of tradition to crowd out what moral sense there is, much in the way that dependency on Waze can cause our internal sense of direction to atrophy.

Modern societies, it should be noted, run a much greater risk. Saturated with scientific thinking, moderns tend to imagine that all wisdom, including moral and religious wisdom, grows only more refined and precise with time, just as science does. This belief in the ubiquity of progress suggests to many people that moral instincts, as well as the traditions they generate, ought to be overcome in favor of a reasoned approach to maximizing societal good. Undervalued moral traditions are thus replaced by overvalued moral theories. The availability of such theories (John Rawls’s A Theory of Justice is a famous example), in conjunction with the atrophy of the moral sense, can lead to the identification of morality with some theory altogether untethered from any moral tradition and the original sense that launched it.

This is precisely the pitfall that traditional Judaism must avoid, and as a rule strives to avoid. In this respect, it possesses one decided advantage. Although the exercise of codifying and refining tradition can appear to some to be merely technical in nature, and sometimes even morally arbitrary, the very fact of Judaism’s own radical conservatism is what keeps it tethered to the moral message of its prophetic origins.

The modern mind, with its high-spectrum focus, is tempted by models: a truncated model of the human mind becomes conflated with the real thing, and a truncated model of morality becomes conflated with the real thing. David Gelernter’s The Tides of Mind is a welcome reminder that we yield to this temptation at our peril.

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