Welcome to Chapter 1 of The Beginning of Infinity by David Deutsch: The Reach of Explanations. If you step outside on a clear night and look up, the universe appears tiny, serene, and cold. To unaided human eyes, the cosmos is just a dark dome pinned with a few thousand twinkling points of light. For tens of thousands of years, humans looked at those lights and believed what their senses told them. But David Deutsch opens this monumental book with a staggering paradox. Today, we know that those twinkling sparks are not cold lights at all. Some of them are quasars—cosmic monsters powered by supermassive black holes, shining brighter than a trillion suns, billions of light-years away. We know that inside distant stars, lighter elements are undergoing transmutation through thermonuclear fusion, forging the very atoms that make up our bodies. Now, ask yourself: How do we actually know that? No human has ever visited a star. We cannot touch stellar plasma or capture a piece of a quasar in a test tube. All that ever reaches our planet is a faint drizzle of light striking a telescope mirror or the retina of an eye. How is it possible that creatures trapped on the surface of a tiny rock can possess reliable, detailed knowledge about the unseen reality of the cosmos? For centuries, common sense and conventional philosophy gave a confident answer: Empiricism. Philosophers like John Locke claimed that the human mind begins as a white paper, a blank slate, and that all knowledge is derived from sensory experience. 经验主义告诉我们：看多了，观察久了，自然就能总结出规律。This naturally led to Inductivism—the widespread belief that scientific theories are built by generalizing repeated observations into universal laws. If you see the sun rise every morning, you induct that the sun always rises. Deutsch dismantles this entire worldview with surgical precision. First of all, induction is not just flawed—it does not exist. 归纳法从来没有真正发生过。 As the ancient philosopher Heraclitus famously said, no man ever steps in the same river twice. No two experiences are ever identical. The sun never rises under the exact same cosmic conditions. If you think the future will resemble the past simply because it has done so before, you are falling into the trap of Bertrand Russell’s inductivist turkey. The turkey was fed every single morning at nine o’clock. Following the laws of induction, it calculated that being fed was a universal law of nature—until the morning of Thanksgiving, when its throat was cut. Second, Deutsch points out that there is no such thing as raw, unbiased observation. Observation is always theory-laden. 我们的观察永远浸透着理论。 When you look at the sky, your senses tell you that the Earth is flat, stationary, and that the sun is traveling overhead. If science were derived purely from the senses, astronomy would have been permanently stuck. Senses do not perceive theories; senses perceive raw physical phenomena that can only be understood after being filtered through layers of conscious and unconscious interpretation. So if knowledge does not come from the senses, where does it come from? Deutsch’s answer is profound: All knowledge begins with creative conjecture. 所有的知识，源头全都是人类大脑大胆的猜想。 We do not derive theories from facts. We invent theories through wild creative leaps to explain what might be going on behind the appearances. And what is the role of experiments? Experiments do not generate theories; they are elimination tools. 实验从来不是用来制造理论的，实验是用来在互相竞争的猜想中无情淘汰错误的。Science advances through a perpetual cycle of conjecture alternating with criticism. This brings us to the ancient epistemological trap: Justificationism. For thousands of years, humans believed that knowledge was only valid if it was certified by some infallible authority—whether that was holy scripture, ancient tradition, or philosophical dogma. But Deutsch aligns himself with Karl Popper’s fallibilism. Fallibilism recognizes that there are no authoritative sources of knowledge, and we can never achieve absolute certainty. 任何权威都会犯错，任何知识都可能在未来被推翻。 True progress does not come from proving you are right. True progress comes from building systems that relentlessly correct errors. And this brings Deutsch to the central criterion of the entire book: What makes a good explanation? First, what is an explanation? An explanation is an assertion about the unseen reality that accounts for seen appearances. 解释，就是去揭示那套支配表象的深层机制。 Most explanations in human history have been bad explanations. And Deutsch defines a bad explanation with a brilliant concept: An explanation that is easy to vary. 一个容易被随意篡改的解释，就是坏解释。 Look at how the ancient Greeks explained the seasons. The myth went that Hades, god of the underworld, kidnapped Persephone, the goddess of spring. Her mother Demeter, the goddess of agriculture, was so grief-stricken that she cursed the earth, causing vegetation to die and bringing winter. When Persephone was allowed to return for six months, Demeter rejoiced, and spring returned. Why is this a terrible explanation? Because it is infinitely pliable. If someone objected that it doesn't make sense for a mother's grief to create cold weather, you could easily replace grief with anger. If winter arrived earlier, you could claim Hades threw a tantrum. If ancient Greeks had sailed to Australia and discovered that winter in the south occurs during northern summer, they could easily invent another goddess to patch the story. You can swap out the gods, alter the plot, and the myth still pretends to explain the seasons. An explanation that can easily accommodate anything ultimately explains nothing. Now, contrast that with the real explanation discovered during the Scientific Revolution: the seasons are caused by the Earth’s 23.5-degree axial tilt as it orbits the sun. This explanation is hard to vary. Every single part of the geometric model is tightly locked in place. If you try to change the tilt to 30 degrees, the predicted solar angles collapse. If you try to claim the sun is closer in summer, the fact that Australia experiences summer when the UK is in freezing winter destroys your claim. Every detail in a good explanation is tightly constrained by reality. You cannot casually alter a single parameter without ruining the entire explanatory mechanism. And this leads to the magical phenomenon that gives this chapter its title: The Reach of Explanations. When a theory is hard to vary, its tight internal gears give it an astonishing property that no one deliberately designed: reach. 一个高质量的好解释，其解释力会远远超出它最初被创造出来的那个小问题。 Think about it: the 23.5-degree axial tilt theory was originally devised solely to explain why seasons change on Earth. But because it was a hard-to-vary explanation rooted in the objective geometry of celestial motion, it suddenly explained seasons on Mars. It explained the behavior of exoplanets billions of miles away. It explained climate cycles across millions of years. This is the great revelation of Chapter 1. For almost all of human history, our species was trapped in a static loop of easy-to-vary myths and dogmas. There were brief flashes of light—the mini-enlightenments of Ancient Athens or Renaissance Florence—but they were always extinguished because they lacked an institutional tradition of open criticism. The Scientific Revolution and the Enlightenment changed the trajectory of the universe forever. Not because humans suddenly grew smarter, but because we discovered a new way of pursuing knowledge: the rebellion against authority in favor of error-correction, and the relentless search for explanations that are hard to vary. That transition was not just another historical event. It was the moment human civilization crossed an ontological threshold. It was the beginning of infinity. As long as the laws of physics do not prohibit something, and as long as we know how to maintain the tradition of conjecture, criticism, and seeking good explanations, any problem is soluble. There is no natural limit to human progress, and we are standing at the very first step of an endless frontier.