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I Thinking from First Principles?

  1. Mar 29, 2016 #1
    I've reflected a lot on the concept of thinking from First Principles. I've been reading about the subject but I can't find good references.
    So far, I'm able to summarize what I've found to the latter question: "What are we sure is true about this?"
    I was wondering if there was more to it. I believe this is a Physic Framework and I hope this is the right place to ask the latter questions.
    Are there reference anyone would recommend on this (may it be a passage of a certain book or some websites/blogs)? Are you using this mental framework regularly? When?
  2. jcsd
  3. Mar 29, 2016 #2
    Hi and welcome to PF!
    What is? Thinking from first principles? Certain aspects of physics defy sound classical descriptions. It's not a failure of the model, it's simply a limit of it's applicability.
  4. Mar 29, 2016 #3
    First principles are the fundamental laws and concepts from which everything else is derived, so by fundamental we mean it can't be explained more simply in terms of anything else. Alternatively, we trust someone else to do the derivation and look up the final result in a book.
  5. Mar 30, 2016 #4
    You mean like Elon Musk recommends, right? Start with "first principles" - that is, "what we are sure is true". Don't "reason by analogy". They mean the same thing: don't take authority's word for it, go back to fundamentals and reason for yourself. That's just what good thinkers do automatically ... sometimes.

    Physics relates to the issue in two ways. One, physicists need to follow this advice (sometimes) also. Two, physics has always provided laypersons with the "first principles" of reality itself, relevant to any undertaking: entrepreneurial, philosophical, whatever.

    The flip side of "first principles thinking" however is: you have to take authority's word for it anyway, most of the time. You can't always figure it out for yourself from the ground up. In that case you'd still be trying to understand what food is good for - since you didn't accept Mom's advice on the topic. Or you'd be in jail trying to understand, from first principles, why you should follow laws. You'll be a lousy student if you don't just believe the teacher most of the time. S/he'll be very happy to see you think things through for yourself - after doing all the assigned problems! Scientists often have to believe other's results, can't check everything yourself, you'd never get anywhere

    "Believe" experts and act accordingly, while always questioning and understanding why they said that. When you realize they're wrong reject them, but until then - the fact is, they're probably right.

    The first principles of physics for a physicist means the fundamental laws - Thermodynamics, Newton, Maxwell, SR, GR etc.

    But for general use they're more basic. Time, space, matter, light, motion etc are the "first principles" of physics for non-physicists. Thinking about what they really mean will help in any endeavor. Read Aristotle, Kant, and so forth. All the great philosophers are worth looking at. By the way don't get caught up in pop-science about multiple universes and such; completely useless.

    That's not to say real physics is irrelevant for a layperson (like myself, for instance). In the modern world the basics of electricity are important; also mechanical systems. Even more sophisticated ideas like thermodynamics and geophysics are useful for understanding issues like global warming. If nothing else it's very interesting.

    I don't know any good blogs that talk about this sort of thing but I checked on google, didn't see any meat.

    There are no simple fool-proof rules for "how to think". Learn by doing.
    Last edited: Mar 30, 2016
  6. Apr 2, 2016 #5
    Very interesting insight. Thanks for sharing!

    From what I understand of your posts, one may think by first principles only when there are good reasons to doubt existing paradigms.

    May I ask why you think they are useless? I've never really followed the evolving theories around multiverse but I'm assuming first principles thinking is involved in the process.

    I was in the impact such "way to think" could have on the learning process. As Albert Einstein says: "Information is not knowledge".
    I'm a college student and it hits me how we're not thought to reflect (maybe it's just my program/school and all the schools I went to in my life). Where you would need to ask yourself questions, there seems to be a natural tendency to simply lookup the answer. Maybe thinking from first principles is way to introduce more reflectiveness and less cognitive laziness.

    Anyway, thanks for your answer, it's truly appreciated.
  7. Apr 2, 2016 #6


    Staff: Mentor

    IMO an explicit lesson in critical thinking should be given to all HS and college students. Here is my feeble definition.

    When you hear something, you should think about why you should our shouldn't believe it.
    • Consider the reputation and credentials of the source.
    • Question how the source, or anyone, knows what he said is true. Some things are nearly unknowable.
    • What motivations might the source have to say what he did?
    • What cooberading evidence do you know that support or refute what was said.
    • Did the speaker express opinion or fact? Opinion can't be subject to a true /false test but we can still decide whether or not to be influenced by it.
    • Something is a fact only if it can be verified by an independent source. People's strong opinions can never establish a fact.
    If you do all that you may find good reason to believe our disbelieve what was said. Other times, your critical thinking may not be helpful at all, leaving no guidance on whether you should believe. It is only human to be biased to believe everything you hear. So, even though critical thinking does not always help, it is smart to always try it.

    That small lesson, plus a couple of examples could be completed in only 30 minutes of class time IMO.
  8. Apr 2, 2016 #7
    Sorry about this anorlunda when you say. Something is a fact only if it can be verified by an independent source. People's strong opinions can never establish a fact.
    Don't you actually mean . Peoples strong opinions can never establish a fact unless it can be verified by an independent source.
    A person or people can hold strong opinions and they can still be established as fact, for example the strong opinions they held were factual and right all along, once checked out.
  9. Apr 2, 2016 #8


    Staff: Mentor

    If they can be verified , they can be a fact. My point was that no matter how strongly someone believes something is true, that does not make it a fact unless it can be verified.

    People tend to mix up truth with factual.
  10. Apr 3, 2016 #9
    Thanks so much for sharing this anorlunda.

    I usually try to classify the information into four categories (complete, misinformed, incomplete, uninformed - From How to Read a Book). I feel like your practical tips you just offered are extremely complementary to this.

    The fact that you can decide when it is relevant to think from first principles by thinking critically is truly insightful and I really appreciate the time you took to answer this!
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