Why Immanuel Kant Still Has More to Teach Us

That may not exactly sound like a call to arms, but the title of an expert and engaging new introduction to the philosopher encourages us to think otherwise. “Kant: A Revolution in Thinking” (Harvard), by Marcus Willaschek, translated by Peter Lewis, argues that what made Kant revolutionary was his contention that to understand anything—science, justice, freedom, God—we first have to understand ourselves. Willaschek, one of the world’s leading authorities on Kant and the editor of the standard German edition of Kant’s works, writes, “Kant placed the human at the center of his thought like no other philosopher before him.” As Willaschek demonstrates, Kant believed that his ideas would change humanity’s understanding of its place in the world as profoundly as the Copernican revolution had changed our sense of Earth’s place in the cosmos.

And they did, for philosophy at least, igniting the most fertile period in Western thought since Plato and Aristotle. Willaschek offers a gauge of Kant’s influence by looking at the term “critique,” which Kant used in the titles of his three major books: the “Critique of Pure Reason” (1781), the “Critique of Practical Reason” (1788), and the “Critique of Judgment” (1790). At the time, the word Kritik was a relatively new addition to the German language, and Kant was the first to use it in a title. Today, Willaschek writes, “the catalog of the German National Library contains no fewer than twenty-four thousand works with the word ‘Kritik’ in their titles.”

More broadly, he observes, Kant’s ideas about the mind shaped the development of “psychology, anthropology, and the more recent social sciences.” In the twentieth century, philosophers of science grappled with Kant as they tried to make sense of the baffling discoveries of relativity and quantum physics. The American transcendentalists took their name from one of Kant’s key technical terms: “I apply the term transcendental,” he wrote, “to all knowledge which is not so much occupied with objects as with the mode of our cognition of these objects.” Ralph Waldo Emerson was thus waxing Kantian when he declared, “I become a transparent Eyeball; I am nothing; I see all.”

The central insight that these disparate thinkers took from Kant is that the world isn’t simply a thing, or a collection of things, given to us to perceive. Rather, our minds help create the reality we experience. In particular, Kant argued that time, space, and causality, which we ordinarily take for granted as the most basic aspects of the world, are better understood as forms imposed on the world by the human mind.

The parallel with Copernicus turns out to be apt. Before Copernicus and Kepler and Galileo, people assumed that the sun and the planets revolved around the Earth, and justifiably so—that’s how it appears to us when we look up at the sky. It took a lot of close observation and ingenious reasoning for astronomers to understand that this was a trick of perspective, and that in fact it is the Earth that revolves around the sun. Similarly, it is natural for human beings to assume that the way the world appears to us—extended in three dimensions, constantly moving from the past into the future, changing as its different elements interact—is the way it really is. But, Kant maintained, this is also a trick of perspective. Space and time do not exist objectively, only subjectively, as forms of our experience. He wrote that it is “from the human point of view only that we can speak of space, extended objects, etc.”

This thinking led Kant to a more pessimistic conclusion than Copernicus’s. Whereas humanity did eventually arrive at a correct understanding of the solar system, it is impossible for us to ever know “things in themselves”—what Kant called “noumena.” We have access only to “phenomena”—the way things look to us, given the kind of mind we have. “What things may be in themselves, I know not and need not know, because a thing is never presented to me otherwise than as a phenomenon,” Kant insisted.

This is an “unsettling” message, Willaschek writes: “It seems to rob all the things around us of their solidity, so to speak, and to transform them into mere figments of our imagination.” In fact, Kant didn’t intend to make us doubt the evidence of our senses. Instead, he reasoned, it is because all human beings experience the world through the same categories of time and space that scientific knowledge is possible. Science claims to deal with the world only as we perceive it, not as it is “in itself,” and to that extent it is completely reliable. Anyone who measures an object in free fall in a vacuum will find that it accelerates at thirty-two feet per second squared; we don’t have to worry that this is a “figment of our imagination.”