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344 pages, Hardcover
Published May 28, 2024
The most simple and fundamental advice you can give to people who want to understand math, which I've repeated throughout this book, is to pretend the things are really there, right in front of you, and that you can reach out and touch them. People who don't understand math are basically stuck in a state of disbelief. They're refusing to imagine things that don't actually exist, because they don't see the point. It just makes no sense to them.
There are no tricks. There never were any and there never will be. Believing in the existence of tricks is as toxic as believing in the existence of truths that are counterintuitive by nature.
Believing that tricks exist is to accept the idea that there are things you'll never understand and that you have to learn by heart.
The language trap is the belief that naming things is enough to make them exist, and we can dispense with the effort of really imagining them.
Naming things certainly allows us to evoke them, but not to make them present in our mind with the intensity and clarity that allow for creative thinking.
Mathematics is a practice rather than knowledge. Mathematicians understand better than anyone the objects they're working on, but their mathematical intuition can never become omnipotent.
mathematicians have a saying, that the only thing a math lesson is good for is to allow the professor to understand.
No one can doubt on a piece of paper. Doubt is a secret motor activity, an unseen action. To doubt something is to be able to imagine a scenario, even seemingly improbable, where the thing could be untrue.
Trusting reason too much, using human language as if it had all the attributes of mathematical language, as if words had a precise meaning, as if each detail merited being interpreted and the logical validity of an argument sufficed to guarantee the validity of its conclusions, is a characteristic symptom of paranoia. When applied outside of mathematics and without any safeguards, mathematical reasoning becomes an actual illness.
you can spend twenty years of your life reverse-engineering cars, but that won't teach you anything about traffic jams. And yet traffic jams exist and they're entirely made up of cars.
Successful math becomes so intuitive that it no longer looks like math.
If you find that the math you do understand is too easy, it's not because it's easy, it's because you understand it.
discovery always begins with the simple and innocent desire to understand.
Math is mysterious and difficult because you can't see how others are doing it.
At a profound level, math is the only successful attempt by humanity to speak with precision about things that we can't point to with our fingers.
In a math book, the most important passages aren't the theorems or the proofs: they are the definitions.
The ability to associate imaginary physical sensations with abstract concepts is called synesthesia. Some people see letters in colors. Others see the days of the week as if they were positioned in the space around them.
“Finding mistakes is a crucial moment, above all a creative moment, in all work of discovery, whether it's in mathematics or within oneself. It's a moment when our knowledge of the thing being examined is suddenly renewed.”
Logic doesn't help you think. It helps you find out where you're thinking wrong.
Mathematical writing is the work of transcribing a living (but confused, unstable, nonverbal) intuition into a precise and stable (but as dead as a fossil) text.
When you see things that others don't yet perceive, sharing your vision requires finding a way to get others to re-create those things in their own heads. A mathematical definition serves this purpose. It provides detailed instructions allowing others, starting with things they are already able to see, to mentally construct those new things.
As Thurston remarked, “There is sometimes a huge expansion factor in translating from the encoding in my own thinking to something that can be conveyed to someone else.”
Mathematical comprehension is precisely this: finding the means of creating within yourself the right mental images in place of a formal definition, to turn this definition into something intuitive, to “feel” what it is really talking about.
Visual intuition makes certain mathematical properties clear, that without the mental image wouldn't be clear at all. This is why transforming mathematical definitions into mental images is so important. When you're unable to imagine mathematical objects, you have the sense that you don't really understand them. And you'd be right.
Reasoning with letters was a way of reasoning with all numbers at once. It was doing an infinite number of computations with a finite number of words.
When we believe we're directly seeing the world in three dimensions, we're unconsciously piecing together the two-dimensional images captured by our retinas.
A conjecture is a mathematical statement that someone believes is valid but isn't yet able to prove. Making a conjecture is feeling something is right without being able to say why. It is by nature a visionary and intuitive act.
Nothing is counterintuitive by nature: something is only ever counterintuitive temporarily, until you've found means to make it intuitive.
Understanding something is making it intuitive for yourself. Explaining something to others is proposing simple ways of making it intuitive.
In mathematics, the sudden occurrence of a miracle or an idea that seems to come out of nowhere is always the signal that you're missing an image.
It's only through a relentless confrontation with doubt that forces you to clarify and specify each detail until it all becomes transparent that you're finally able to create obviousness. Doubt is a technique of mental clarification. It serves to construct rather than destroy.
Thurston's response offers a radical change of perspective: The product of mathematics is clarity and understanding. Not theorems, by themselves. The world does not suffer from an oversupply of clarity and understanding (to put it mildly). The real satisfaction from mathematics is in learning from others and sharing with others. All of us have clear understanding of a few things and murky concepts of many more. There is no way to run out of ideas in need of clarification.
Being a paradox is always a temporary status, in wait of a resolution. Presenting a problem as structurally being a paradox is just a pompous way of saying you can't solve it.
When you mathematically model a deep-learning system, you can define a numerical quantity that measures its “perplexity” in a given situation. A system that learns is one that adjusts its weights in order to reduce its perplexity.
lines written by Thurston in 2011: “Mathematics is commonly thought to be the pursuit of universal truths, of patterns that are not anchored to any single fixed context. But on a deeper level the goal of mathematics is to develop enhanced ways for humans to see and think about the world. Mathematics is a transforming journey, and progress in it can be better measured by changes in how we think than by the external truths we discover.”
“Calculation” comes from the Latin calculus, which means “small pebble,” referring to the stones used on an abacus for counting.