Ling's Notes

First Principles

6 min read

Learning from first principle

Learning from first principles means stripping away “this is how it’s done” and rebuilding your understanding from basic truths you can justify yourself.12

What “first principles” actually means

  • It is a way of thinking where you break a problem or topic into its fundamental components, then reason upward from those.23
  • Instead of copying existing methods (analogies, best practices, standard curricula), you ask what is absolutely true, what is just habit, and what follows logically from the basics.41
  • Elon Musk popularised this in business and engineering by breaking complex things (like rockets, batteries, car costs) into raw materials, physics, and constraints, then designing from there.532

A simple illustration: rather than asking “How do I build a better horse carriage?”, you ask “What is transportation fundamentally? Move people from A to B, with safety, speed, cost, comfort constraints” and you may end up with a car instead of a better carriage.67

The core steps (general recipe)

Most guides converge on a similar practical loop you can apply to anything.3714

  1. Clarify the problem or question
    • State what you’re trying to understand or improve in one clear sentence.83
    • Example: “I want to understand how learning actually works so I can study more effectively.”
  2. List and question your assumptions
    • Write down what you “think you know” or what everyone seems to believe about this topic.143
    • For each item, ask:
      • “How do I know this is true?”
      • “What if the opposite were true?”431
  3. Deconstruct to fundamental truths
    • Break the topic into the simplest elements that are as close as possible to facts of reality: physics, biology, logic, basic data, clear cause–effect.723
    • Fundamental truths are things you could defend with evidence or clear reasoning, not just “everyone says so.”314
  4. Rebuild from the ground up
    • Starting only from your fundamentals, reconstruct an explanation, method, or plan.273
    • Ask: “Given only these basics, what follows? What’s the simplest solution that fits them?”23
  5. Test, get feedback, refine
    • Try your new understanding or method in reality, observe results, then adjust your fundamentals or reasoning if needed.53

How to use it to learn any subject

Here’s how to apply this when learning something new (math, physics, programming, finance, etc.).973

  1. Start with ultra-basic questions
    • “What is this thing, in the simplest possible terms?”
    • “What problem is this concept solving?”7
    • Example (calculus): “A derivative is fundamentally a way to describe how fast something changes.”
  2. Build a minimal foundation
    • Identify the prerequisite ideas you genuinely need, and learn those clearly (even if it means going “backwards” to simpler topics).937
    • Use the Feynman approach: try explaining the concept as if to a child; gaps reveal what is not fundamental or not understood yet.7
  3. Constantly interrogate explanations
    • When you read or watch something, pause and ask:
      • “Which parts are definitions or conventions, and which parts are unavoidable truths?”
      • “Could this be different in another system or context?”143
  4. Connect to reality and intuition
    • Tie concepts to real or visual examples until they “click”.97
    • Example: for probability, think in terms of games, lotteries, or real-life risks; for physics, think in terms of everyday forces and motions.9
  5. Practice “why” chains
    • Use “Five Whys” or similar: keep asking “why?” until you hit something you can’t reasonably question further (a first principle or definition).3
    • Example:
      • “Why do spaced repetitions help memory?” → Because repeated recall strengthens neural connections.
      • “Why does recall matter?” → Because memory is about reactivating patterns of activity in the brain, and practice makes them easier to trigger.

Concrete daily exercises to build the habit

To learn how to learn from first principles, turning it into a daily habit is crucial.3

Try these simple exercises:

  • One-problem deconstruction (5–10 minutes)
    • Pick any small problem (how you organise your day, why you procrastinate, how you cook something).
    • Write: problem → assumptions → fundamentals → one improved solution.83
  • Explain-it-like-I’m-10 journal
    • After studying something, write a one-paragraph explanation as if to a child.
    • Highlight any sentence where you hid behind jargon; revisit that part of the material.7
  • “Opposite day”
    • Take a common belief in your field (“you must take notes by hand”, “you need 8 hours to be productive”, etc.).
    • Argue the opposite for a few minutes; look for data or cases that support it.413
  • Weekly “rebuild”
    • Once a week, choose one skill or topic you use often (how you study, how you work out, how you manage tasks).
    • Strip it to fundamentals and redesign your method from scratch.23

Example: learning more effectively (from first principles)

Let’s walk through a quick example applying this to “how to study”.

  1. Clarify
    • “I want to learn faster and remember more from what I read.”
  2. Question assumptions
    • Assumptions might include: “Re-reading is good studying”, “long sessions are better than short ones”, “highlighting equals learning.”14
  3. Deconstruct learning to fundamentals
    • Basic truths from cognitive science:
      • Memory improves with active recall, not just exposure.
      • Spaced repetition beats cramming.
      • Understanding (connecting ideas) leads to longer retention than rote memorisation.397
  4. Rebuild a study method
    • From those fundamentals, a study system might be:
      • Short sessions with frequent recall (close the book and explain from memory).
      • Use flashcards spaced over days instead of single long cram sessions.
      • After reading, make a simple concept map linking ideas instead of just highlighting.973
  5. Test and refine
    • Try this for two weeks, track how much you remember on quick self-tests, then adjust which tactics actually move the needle.

If you repeat this pattern on different parts of your life, you train yourself to default to first principles thinking rather than habits or expert “scripts”.73

What area do you most want to apply first-principles learning to right now (e.g., math, career decisions, productivity, something else)? 10

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Footnotes

  1. https://fs.blog/first-principles/ ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9

  2. https://blog.btrax.com/first-principles-thinking/ ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7

  3. https://www.maray.ai/posts/first-principles-thinking ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11 ↩12 ↩13 ↩14 ↩15 ↩16 ↩17 ↩18 ↩19 ↩20 ↩21 ↩22

  4. https://www.readynorth.com/blog/what-is-first-principles-thinking ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8

  5. https://theinvisiblementor.com/using-first-principles-to-approach-difficult-problems-like-elon-musk/ ↩ ↩2

  6. https://www.youtube.com/watch?v=NV3sBlRgzTI ↩

  7. https://modelthinkers.com/mental-model/first-principle-thinking ↩ ↩2 ↩3 ↩4 ↩5 ↩6 ↩7 ↩8 ↩9 ↩10 ↩11 ↩12 ↩13

  8. https://www.rhysthedavies.com/first-principle-thinking/ ↩ ↩2

  9. https://www.reddit.com/r/Physics/comments/11nrl20/how_do_i_embrace_the_first_principles_reasoning/ ↩ ↩2 ↩3 ↩4 ↩5 ↩6

  10. https://www.youtube.com/watch?v=ooTnMMnrOTo ↩

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