in two new instruments that performed similar, though distinct, optical tricks. The combination of lenses in one instrument made distant objects appear nearer, the combination in the other made small objects appear larger; and for the first time in history investigators of nature had at their disposal tools that served as an extension of one of the five human senses. As much as the discoveries themselves, what revolutionized science over the course of the seventeenth century was a new means of discovery and what it signified: There is more to the universe than meets the naked eye.
Who knew? After all, these instruments might easily have revealed nothing beyond what we already knew to be there, and what we already knew to be there might easily have been all there was to know. The naked eye alone didn’t have to be inadequate as a means of investigating nature; the invention of these instruments didn’t have to open two new frontiers. But it was; and they did.
For thousands of years, the number of objects in the heavens had been fixed at six thousand or so. Now, there were … more. Since the Creation, or at least since the Flood, the number of kinds of creatures on Earth, however incalculable as a practical matter, had nonetheless been fixed. Now, there were … more. “There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy”: When Shakespeare wrote these words in 1598 or 1599, at the very cusp of the turn of the seventeenth century, he was referring to the understandable assumption among practitioners of what would soon become the old philosophy that much of what was as yet unknown must remain unknown forever, and for the next three hundred years the practitioners of what they themselves came to call the New Philosophy frequently cited it as the last time in history that someone could have written so confidently about civilization’s continuing ignorance of, and estrangement from, the universe.
Because now all you had to do was look. Through the telescope you could see farther than with the naked eye alone and, by seeing farther, discover new worlds without. Through the microscope you could see deeper than with the naked eye alone and, by seeing deeper, discover new worlds within. By seeing more than meets the naked eye and then seeing yet more, you could discover more.
How much more? It was a logical question for natural philosophers to ask themselves, and the search for an answer that ensued over the next three centuries was nothing if not logical: a systematic pursuit of the truths of nature to the outermost and innermost realms of the universe, until by the turn of the twentieth century the search had reached the very limits of human perception even with the aid of optical instruments, and investigators of nature had begun to wonder: What now? What if there was no more more?
Specifically: Was the great scientific program that had begun three centuries earlier coming to a close? Or would an increasingly fractional examination of the existing evidence continue to reward investigators with further truths?
Some researchers, however, unexpectedly found themselves confronting a third option. Pushing the twin frontiers of scientific research—the inner universe and the outer—they had arrived at an impasse. Then, they’d spanned it. They’d kept looking until they discovered an entirely new kind of scientific evidence: evidence that no manner of mere looking was going to reveal; evidence that lay beyond the realm of the visible; evidence that was, to all appearances, invisible.
The invisible had always been part of humanity’s interactions with nature. Attempting to explain otherwise inexplicable phenomena, the ancients had invented spirits, forms and gods. In the Western world during the medieval era, those various causes of mysterious effects had coalesced into the idea of one God. Even after the inception of the modern era and the inauguration of the scientific method, investigators working at the two extremes of the universe had resorted to two new forms of the invisible. When Isaac Newton reached the limits of his understanding of the outer universe, he had invoked the concept of gravity. When René Descartes reached the limits of his understanding of the inner universe, he had invoked the concept of consciousness.
But by the turn of the twentieth century the kind of invisibility that certain investigators were beginning to invoke was new. These were scientists for whom any appeal to the supernatural, superstitious, or metaphysical would have been anathema. But now, here it was: evidence that was invisible yet scientifically incontrovertible, to their minds, anyway.
Although Einstein and Freud didn’t initiate this second scientific revolution all by themselves, they did come to represent it and in large measure embody it. This is the story of how their respective investigations reached unprecedented realms, relativity and the unconscious; how their further pursuits led to the somewhat inadvertent creation of two new sciences, cosmology and psychoanalysis; and how in Einstein’s case, a new way of doing science has become the dominant methodology throughout the sciences, while in Freud’s case, an alternative way of doing science has become the dominant exception, the key to the very question of what qualifies an intellectual endeavor as a science. This is also the story of what cosmology and psychoanalysis have allowed us to explore: universes, without and within, as vast in comparison to the ones they replaced as those had been to the ones they replaced.
And in that regard Einstein and Freud’s is a story, just as Galileo and Leeuwenhoek’s was, of a revolution in thought. The difference between our vision of the universe and its nineteenth-century counterpart has turned out to be not a question of what had distinguished each previous era from the preceding one for nearly three hundred years: of seeing farther or deeper, of seeing more—of perspective, of how much we see. Instead, it is a question of seeing itself—of perception, of how we see. It is also, then, a question of thinking about seeing—of conception, of how we think about how we see. As much as any discovery, this is what has changed the way we try to make sense of our existence in the twenty-first century—the way we struggle to investigate our circumstances as sentient creatures in a particular setting: Who are these creatures? What is this setting? It is a new means of discovery—the significance of which, a hundred years later, we are still only beginning to comprehend: that there is more to the universe than we would ever find, if all we ever did was look.
Look.
And so the boy looked. His father had something to show him. It was small and round like a miniature clock, the boy saw, but instead of two hands pointing outward from the center of the face it had one iron needle. As the boy continued to look, his father rotated the object. He turned it first one way, then the other, and as he did so the most amazing thing happened. No matter how the boy’s father moved the object, the needle continued pointing in the same direction—not the same direction relative to the rest of the device, as the boy might have expected, but the same direction relative to … something else. Something out there, outside the device, that the boy couldn’t see. The needle was shaking now. It trembled with the effort. Some six decades later, when Albert Einstein recalled this scene, he couldn’t remember whether he had been four or five at the time, but the lesson he’d learned that day he could still summon and summarize crisply: “Something deeply hidden had to be behind things.”
Some things deeply hidden, actually. As the boy grew older, he learned what a few of those deeply hidden somethings were: magnetism, the subject of his father’s demonstration on that memorable day; electricity; and the relationship between the two. He learned that the existence of a relationship between magnetism and electricity was still so recent a discovery that nobody yet understood how it worked, and then he learned that within his lifetime physicists had demonstrated that this relationship manifested itself to our eyes as light. And he learned that even though nobody yet understood how light worked, what everybody did know was that it
