Stanislas Dehaene’s Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts is a compulsively readable summary of the “global neural workspace theory” of consciousness. Chapters 1-2 are an especially useful summary of the last two decades of research into unconscious perception. If you are unfamiliar with the idea that your memories and perception of the world around you—down to the shapes, colors, and items you see in the room you are sitting in—are an incomplete representation of reality, a representation that is equal parts a reflection of data taken in from the outside world by your senses and a series of guesses derived from statistical computations performed by unconsciously your brain, then you should buy and read the book (or at least the first hundred pages). Included in these first hundred pages is a lovely digression where Dehaene launches into harangue upon Sigmund Freud:
The discovery that a dramatic amount of mental processing occurs outside our awareness is generally credited to Sigmund Freud (1856– 1939). However, this is a myth, crafted in large part by Freud himself. As noted by the historian and philosopher Marcel Gauchet, “When Freud declares, in substance, that prior to psychoanalysis the mind was systematically identified with consciousness, we have to declare this statement rigorously false.”
In truth, the realization that many of our mental operations occur sub rosa, and that consciousness is only a thin veneer lying atop sundry unconscious processors, predates Freud by decades or even centuries. In Roman antiquity, the physician Galen (ca. 129– 200) and the philosopher Plotinus (ca. 204– 270) had already noticed that some of the body’s operations, such as walking and breathing, occur without attention. Much of their medical knowledge was in fact inherited from Hippocrates (ca. 460– 377 BC), a keen observer of diseases whose name remains an emblem of the medical profession. Hippocrates wrote an entire treatise on epilepsy, called The Sacred Disease, in which he noted that the body suddenly misbehaves against its owner’s will. He concluded that the brain constantly controls us and covertly weaves the fabric of our mental life:
Men ought to know that from the brain, and from the brain alone, arise our pleasures, joys, laughter and jests, as well as our sorrows, pains, grieves and tears. Through it, in particular, we think, see, hear and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant.
During the Dark Ages, which followed the fall of the Roman Empire, Indian and Arab scholars preserved some of antiquity’s medical wisdom. In the eleventh century, the Arab scientist known as Alhazen (Ibn al-Haytham, 965– 1040) discovered the main principles of visual perception. Centuries before Descartes, he understood that the eye operates as a camera obscura, a receiver rather than an emitter of light, and he foresaw that various illusions could fool our conscious perception. Consciousness was not always in control, Alhazen concluded. He was the first to postulate an automatic process of unconscious inference: unknown to us, the brain jumps to conclusions beyond the available sense data, sometimes causing us to see things that are not there.
Eight centuries later the physicist Hermann von Helmholtz, in his 1867 book, Physiological Optics, would use the very same term, unconscious inference, to describe how our vision automatically computes the best interpretation compatible with incoming sense data.
Beyond the issue of unconscious perception lay the greater issue of the origins of our deepest motives and desires. Centuries before Freud, many philosophers— including Augustine (354– 430), Thomas Aquinas (1225– 74), Descartes (1596– 1650), Spinoza (1632– 77), and Leibniz (1646– 1716)— noted that the course of human actions is driven by a broad array of mechanisms that are inaccessible to introspection, from sensorimotor reflexes to unaware motives and hidden desires. Spinoza cited a hodgepodge of unconscious drives: a child’s desire for milk, an injured person’s will for revenge, a drunkard’s craving for the bottle, and a chatterbox’s uncontrollable speech.
During the eighteenth and nineteenth centuries, the first neurologists discovered proof after proof of the omnipresence of unconscious circuits in the nervous system. Marshall Hall (1790– 1857) pioneered the concept of a “reflex arc,” linking specific sensory inputs to particular motor outputs, and he emphasized our lack of voluntary control over basic movements that originate in the spinal cord. Following in his footsteps, John Hughlings Jackson (1835– 1911) underscored the hierarchical organization of the nervous system, from the brain stem to the cerebral cortex and from automatic operations to increasingly voluntary and conscious ones. In France, the psychologists and sociologists Théodule Ribot (1839– 1916), Gabriel Tarde (1843– 1904), and Pierre Janet (1859– 1947) stressed the broad range of human automatisms, from practical knowledge stored in our action memory (Ribot) to unconscious imitation (Tarde) and even to subconscious goals that date from early childhood and become defining facets of our personality (Janet). French scientists were so advanced that when the ambitious Freud published his first claims to fame, Janet protested that he owned the paternity of many of Freud’s ideas.
As early as 1868, the British psychiatrist Henry Maudsley (1835– 1918) had written that “the most important part of mental action, the essential process on which thinking depends, is unconscious mental activity.” Another contemporary neurologist, Sigmund Exner, who was Freud’s colleague in Vienna, had stated in 1899: “We shouldn’t say ‘I think,’ ‘I feel,’ but rather ‘it thinks in me’ [es denkt in mir], ‘it feels in me’ [es fühlt in mir]”— a full twenty years prior to Freud’s reflections in The Ego and the Id (Das Ich und das Es), published in 1923. At the turn of the century, the ubiquity of unconscious processes was so well accepted that in his major treatise The Principles of Psychology (1890), the great American psychologist and philosopher William James could boldly state:
“All these facts, taken together, form unquestionably the beginning of an inquiry which is destined to throw a new light into the very abysses of our nature. . . . They prove one thing conclusively, namely, that we must never take a person’s testimony, however sincere, that he has felt nothing, as proof positive that no feeling has been there.”
Any human subject, he surmised, “will do all sorts of incongruous things of which he remains quite unaware.” Relative to this flurry of neurological and psychological observations, clearly demonstrating that unconscious mechanisms drive much of our lives, Freud’s own contribution appears speculative. It would not be a huge exaggeration to say that in his work, the ideas that are solid are not his own, while those that are his own are not solid.
The interesting question then is this: if the unconscious nature of human perception and motivation had been so long known, why did Freud’s restatement have such a large impact on his contemporaries? In 1931, Frederick Lewis Allen was ready to credit “the Freudian gospel” with both the collapse of the pre-1920s system of sexual and gender norms and with the general sense of intellectual cynicism that prevailed in that decade. Why did Freud get credit for that instead of the dozens of physicians, philosophers, and psychologists that Dehaene mentions?
Allen’s depiction of popular Freudianism may hold the clue. The cynicism of ’20s intellectuals came from ideas like:
That we are residents of an insignificant satellite of a very average star obscurely placed in one of who-knows-how-many galaxies scattered through space; that our behavior depends largely upon chromosomes and ductless glands; that the Hottentot obeys impulses similar to those which activate the pastor of the First Baptist Church, and is probably already better adapted to his Hottentot environment than he would be if he followed the Baptist code; that sex is the most important thing in life, that inhibitions are not to be tolerated, that sin is an out-of-date term, that most untoward behavior is the result of complexes acquired at an early age, and that men and women are mere bundles of behavior-patterns, anyhow.
Now not all of that came from Freud (“obscurely placed planet”), but the majority does, and falls under Allen’s discussion of what he calls the “Freudian gospel.” The key to Freud’s success, I think, was not that he proposed human action was largely the product of unconscious perceptions, desires, and so forth. That was not new. What was new was Freud’s argument that all of these perceptions, desires, and complexes were the product of the sex drive. Freud changed the intellectual world by boiling human behavior down to sex. The unconscious was just a way stop on that path. It was a tool needed to explain away the incredible variety of emotions and impulses that make up human life.
As with Freud so with many who have followed in his foot steps. You will be told that human behavior is all about ‘X.’ For some people, ‘X’ will be class or racial consciousness; for others it will be power, or social signaling, or some narrowly defined function of expected utility. There is something incredibly seductive in all such tales. It is hard not to be pulled in by the cynical claims of a theory that reduces the totality of human society to a single base impulse. Freud took advantage of this and became famous because of it.
 Stanislas Dehaene, Consciousness and the Brain (New York: Penguin Publishing Group, 2014), 55-56.
 Frederick Lewis Allen, Only Yesterday: An Informal History of the 1920s (Open Road Media, 2015; or. ed. 1931), kindle location 2812.