The so-called "scientific method" is, I think, rather poorly understood. For example, let us consider one of the best-known laws of nature, often simply referred to as the Law of Gravity:
Newton's Law of Universal Gravitation: Every object in the universe attracts every other object toward it with a force proportional to the product of their masses, divided by the square of the distance between their centers of mass.
Now here is a series of questions for you, which I often ask audiences when I give lectures on the philosophy of science:
- Do you believe Newton's Law of Universal Gravitation is true?
- If so, how sure are you that it is true?
- Why do you believe it, with that degree of certainty?
The most common answers to these questions are "yes", "very sure", and "because it has been extensively experimentally verified." Those answers sound reasonable to any child of the Enlightenment -- but I submit, on the contrary, that this set of answers has no objective basis whatsoever. To begin with, let us ask, how many confirming experiments do you think would have been done, to qualify as "extensive experimental verification." I would ask that you, the reader, actually pick a number as a rough, round guess.
Whatever number N you picked, I now challenge you state the rule of inference that allows you to conclude, from N uniform observations, that a given effect is always about from a given alleged cause. If you dust off your stats book and thumb through it, you will find no such rule of inference rule there. What you will find are principles that allow you to conclude from a certain number N of observations that with confidence c, the proportion of positive cases is z, where c < 1 and z < 1. But there is no finite number of observations that would justify, with any nonzero confidence, that any law held universally, without exception (that is, z can never be 1 for any finite number of observations, no matter how small the desired confidence c is, unless c = 0). . And isn't that exactly what laws of nature are supposed to do? For Pete's sake it is called the law of universal gravitation, and it begins with the universal quantifier every (both of which may have seemed pretty innocuous up until now).
Let me repeat myself for clarity: I am not saying that there is no statistical law that would allow you to conclude the law with absolute certainty; absolute certainty is not even on the table. I am saying that there is no statistical law that would justify belief in the law of universal gravitation with even one tenth of one percent of one percent confidence, based on any finite number of observations. My point is that the laws of the physical sciences -- laws like the Ideal gas laws, the laws of gravity, Ohm's law, etc. -- are not based on statistical reasoning and could never be based on statistical reasoning, if they are supposed, with any confidence whatsoever, to hold universally.
So, if the scientific method is not based on the laws of statistics, what is it based on? In fact it is based on the
Principle of Abductive Inference: Given general principle as a hypothesis, if we have tried to experimentally disprove the hypothesis, with no disconfirming experiments, then we may infer that it is likely to be true -- with confidence justified by the ingenuity and diligence that has been exercised in attempting to disprove it.
In layman's terms, if we have tried to find and/or manufacture counterexamples to a hypothesis, extensively and cleverly, and found none, then we should be surprised if we then find a counterexample by accident. That is the essence of the scientific method that underpins most of the corpus of the physical sciences. Note that it is not statistical in nature. The methods of statistics are very different, in that they rest on theorems that justify confidence in those methods, under assumptions corresponding to the premises of the theorems. There is no such theorem for the Principle of Abductive Inference -- nor will there ever be, because, in fact, for reasons I will explain below, it is a miracle that the scientific method works (if it works).
Why would it take a miracle for the scientific method to work? Remember that the confidence with which we are entitled to infer a natural law is a function of the capability and diligence we have exercised in trying to disprove it. Thus, to conclude a general law with some moderate degree of confidence (say, 75%), we must have done due diligence in trying to disprove it, to the degree necessary to justify that level confidence, given the complexity of the system under study. But what in the world entitles us to think that the source code of the universe is so neat and simple, and its human denizens so smart, that we are capable of the diligence that is due?
For an illuminating analogy, consider that software testing is a process of experimentation that is closely analogous to scientific experimentation. In the case of software testing, the hypothesis being tested -- the general law that we are attempting to disconfirm -- is that a given program satisfies its specification for all inputs. Now do you suppose that we could effectively debug Microsoft Office, or gain justified confidence in its correctness with respect to on item of its specification, by letting a weasel crawl around on the keyboard while the software is running, and observing the results? Of course not: the program is far too complex, its behavior too nuanced, and the weasel too dimwitted (no offense to weasels) for that. Now, do you expect the source code of the Universe itself to be simpler and friendlier to the human brain than the source code of MS Office is to the brain of a weasel? That would be a miraculous thing to expect, for the following reason: a priori, if the complexity of that source code could be arbitrarily large. It could be a googleplex lines of spaghetti code -- and that would be a infinitesimally small level of complexity, given the realm of possible complexities -- namely the right-hand side of the number line.
In this light, if the human brain is better equipped to discover the laws of nature than a weasel is to confidently establish the correctness an item in the spec of MS Office, it would be a stunning coincidence. That is looking at it from the side of the a priori expected complexity of the problem, compared to any finite being's ability to solve it. But there is another side to look from, which is the side of the distribution of intelligence levels of the potential problem-solvers themselves. Obviously, a paramecium, for example, is not equipped to discover the laws of physics. Nor is an octopus, nor a turtle, nor a panther, nor an orangutan. In the spectrum of natural intelligences we know of, it just so happens that there is exactly one kind of creature that just barely has the capacity to uncover the laws of nature. It is as if some cosmic Dungeon Master was optimizing the problem from both sides, by making the source code of the universe just simple enough that the smartest beings within it (that we know of) were just barely capable of solving the puzzle. That is just the goldilocks situation that good DM's try to achieve with their puzzles: not so hard they can't be solved, not so easy that the players can't take pride in solving them
There is a salient counterargument I must respond to. It might be argued that, while it is a priori unlikely that any finite being would be capable of profitably employing the scientific method in a randomly constructed universe, it might be claimed that in hindsight of the scientific method having worked for us in this particular universe, we are now entitled, a posteriori, to embrace the Principle of Abductive Inference as a reliable method. My response is that we have no objective reason whatsoever to believe the scientific method has worked in hindsight -- at least not for the purpose of discovering universal laws of nature! I will grant that we have had pretty good luck with science-based engineering in the tiny little spec of the universe observable to us. I will even grant that this justifies the continued use of engineering for practical purposes with relative confidence -- under the laws of statistics, so long as, say, one anomaly per hundred thousand hours of use is an acceptable risk. But this gives no objective reason whatsoever (again under the laws of statistics) to believe that any of the alleged "laws of nature" we talk about is actually a universal law. That is to say, if you believe, with even one percent confidence, that we ever have, or ever will, uncover a single line of the source code of the universe -- a single law of Nature that holds without exception -- then you, my friend, believe in miracles. There is no reason to expect the scientific method to work, and good reason to expect it not to work -- unless human mind was designed to be able to uncover and understand the laws of nature, by Someone who knew exactly how complex they are.
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Notes -
A well thought-out post! However, I reject your Principle of Abductive Inference. The essence of science is falsification. Experiments cannot verify a hypothesis (it always remains just our best guess), but they can contradict and thus falsify a hypothesis. The hypothesis "all swans are white" cannot be verified by any number of white swans (because there may always be a non-white swan out there), but it is contradicted by the observation of a single black swan. Of course, the experiment itself is also just a best guess (maybe the swan is just painted black?). All knowledge is guesswork. However, the logical relationship of falsification holds (the hypothesis is logically contradicted by the experiement), while inductive inference is not logically sound (no amount of verification can "ground", "prove" or whatnot that the hypothesis is true).
For further reading along these lines, I recommend "The Logic of Scientific Discovery" by Karl Popper, or this shorter and more modern article: https://www.science.org/doi/10.1126/science.284.5420.1625
To answer your three questions:
Yes, I believe Newton's Law of Universal Gravitation is true.
How sure am I that it is true? Psychologically, very sure. Logically and rationally speaking, not at all, it's just a guess.
Why do I believe it, and with that degree of certainty? I believe it beause it has passed tests that other competing hypotheses have failed. This does not prove it to be true (with any degree of certainty), as you rightly point out, but given we accept the results of the tests, it makes it preferable to the competing hypotheses that fail those tests, because they are logically contradicted by those tests. So it's our best guess because its competitors have been eliminated by experiments, but it is not certain or probable or verified in any way.
Really, you are very close to my position on this, except you want experiments to do more than they can do, and struggling to find a way for them to do what they cannot, namely provide justification/inference/certainty/likelihood for hypotheses. Experiments can contradict and thus falsify hypotheses, but they cannot justify them. Relinquish the demand for justification, and the logical situation is clean and sound: we make guesses, discard those guesses that don't stand up to experiments, and tentatively accept those that do.
Thanks for the reply.
I agree that my argument does not merit against your stated belief [Newton's L.O.G is (merely) our best guess for how gravity works]. But I submit that you have good reason to believe something stronger than your stated belief, that in your heart you do believe something stronger than that (as you indicate: " Psychologically, very sure."), that you probably act as if you believe something stronger than that, and that you plan to deliberately continue acting that way. So, either you are acting irrationally (which I doubt), or something is missing from your formal statement (which I submit is probably the case).
For example, imagine you are told that a certain missile defense system uses a model of rocket flight that is based on Newton's law of gravity. Do you think it would be rational to posit that the system is unsafe, and to take costly action to avoid relying on it, specifically on the grounds that Newton's law of gravity is a "just a guess" in which we are not entitled to a smidgeon of confidence? Now, by comparison, imagine that a system protecting your safety were based on the latest theory of a less well studied domain (say, quantum computing); in that case you might be justifiably concerned about that, and, if so, be more likely to take costly actions to avoid relying on that system -- even though the theory it rests on, like Newton's law of gravity, might be our current best guess about the relevant domain.
Here is the point: (1) we have best guesses in many different domains of inquiry; (2) we have more confidence in our best guesses in some domains than we do in others, and (3) it is prima facie instrumentally rational to act on those differences. So, if our stated beliefs are to be consistent with our actions, which we fully intend to continue taking while regarding ourselves as rational, then we should be able to say something stronger than that the law of gravity is merely our best guess in the relevant domain. If we find ourselves unable to justify saying anything stronger, then we have important epistemological work to do.
As I recall, Popper held that repeated, failed attempts to disprove a hypothesis count as evidence for its truth (though never certain evidence). Am I mistaken?
The first thing I should clarify is that I think that scientific hypotheses, despite evidence never being able to elevate them above the status of a guess, can be true, really, absolutely true. If we guess right! So if you say aliens exist and I say they don't, we are both guessing (but not randomly: we are motivated, but not justified, by our other other background beliefs). But either aliens exist or they don't. So despite both of us just guessing, one of us is right and has hit upon the truth, the absolute truth. So while Newton's L.O.G. is just a guess from an epistemological standpoint, I am also tentatively accepting it as true. I claim it really is true, and I act upon that belief, although my belief in that is just a guess. Does that satisfy what you felt was missing from my position?
As for your question on the missile defense systems example. So lets say I'm choosing between two courses of action based on two different scientific hypotheses. If one of those hypotheses has passed its empirical tests and the other hasn't, the logical situation is very clear: logic and reason dictate that I reject the hypothesis that has been falsified by the tests, since the tests logically contradict the hypothesis. The hypothesis that has passed its tests I can tentatively accept as true, and I prefer the course of action based on that hypothesis. If both hypotheses have passed all their tests, I would try to concieve of a test that distinguishes between them (a test that one fails but the other doesn't). If this is not possible, then the logical situation is also clear, however: if both hypotheses have passed all their tests, the evidence tells us exactly nothing about which one we should accept - we have to decide what to believe.
And this is a crucial aspect of my position: rationality and and logic cannot tell us what to believe: we have to make that decision. Reason can, however, tell us what not to believe: we should not believe contradictory things, or in this case hypotheses that are contradicted by test results we accept. Rationality does not provide justifications that tell us what to believe. Rationality is the method, namely the method of critical evaluation and when possible empirical testing, which serves to eliminate some of our ideas, hopefully leaving us with true ones. Yes, it'd be great if we could be justified in believing what we believe, but we can't. So we are left with conjectures that we attempt to parse from error by criticism and empirical testing, using logic and reason, with the goal of believing true things. We are rational, in the sense that we use reason and logic to criticize our ideas and hopefully eliminate errors, and our goal is the truth - we aim at having true beliefs. But we can never know that our beliefs are true; we can only guess at the truth, and use reason as best we can to eliminate the guesses that are untrue.
Does this answer your questions? Feel free to ask more if I've been unclear. There are various complications I didn't want to go into (like differences in the severity of empirical tests) for the sake of clarity.
You are mistaken, but it's a common mistake. In Popper's and my view, corroborating evidence does nothing, but contradicting evidence falsifies (although also without any degree of certainty).
The fact that you have guessed right, or that you may have guessed right, does not entail that you are rationally licensed to embrace the proposition (I think you agree with this). For example, if a tarot card reader told me that I was going to get a job offer today, and I believed her and acted on it by taking out a car loan, and if the Gypsy turned out to be right by sheer luck, my action would still be irrational.
To clarify my position in this light, I never said that the physical laws we have in our corpus are all false, or anything of that sort. I said that we are not entitled to any rational confidence in them -- just as I am not entitled to any rational confidence in a tarot card reading (unless I am mistaken about that practice), even though they may be sometimes right as well -- except to the extent we also believe in miracles.
Success rates matter.
If tarot reading worked as consistently physics or math then boy would that be something.
(Now social sciences, well…)
Science as a method frequently involves guessing and dumb luck and accidental discovery. But then the point is systematically testing findings and examining new evidence and ideas. Tarot reading doesn’t have iterative improvement going on.
The success rate of science in enabling improvements to our material lives is pretty good. The success rate of science in yielding justifiable nonzero confidence in universal natural laws may be zero. Can you defend the proposition that it is not? It would be a compelling refutation of my argument if someone were to give a single universal natural law of the physical world -- take your pick -- and give an objective argument why we should have greater than zero confidence in its literal truth. Now that I think about it, that is the straightforward path to refuting my argument, and it is notable that one has attempted to take it.
A word of advice if you proceed: don't waste your time trying to use Bayesian reasoning; you will not get a nonzero posterior unless you have a nonzero prior, and that would be begging the question. And don't bother trying to use parametric statistics, because no finite number of observations will get you there.
I’m failing to understand why this is a bar any epistemology needs to clear.
Science as a method verifiably works at improving our material lives because it produces sufficiently accurate information. The utility is the payoff, but the correlation to reality is what enables it.
Where does math fit here under “physical world”?
The thing you seem to be doing is putting forth a standard no epistemology can satisfy. It’s not like pure math and logic don’t have identified paradoxes and limitations. Just ask Bertrand Russell.
How about the finding that nothing with mass can exceed the speed of light? This is something backed by math and logic, as well as experimentation. If it were otherwise physics would break, is my layman’s understanding anyway.
Is that sufficiently “universal”?
There are a lot of “universal” rules in physics, so long as you stay at the atomic level. (The quantum domain also has its rules, but they don’t break the atomic ones altogether.)
It sure is. Thanks for taking me up on the offer.
I am looking for objective evidence of the theory, Nullius in verba [Latin: No one's words (will be trusted)]. If you claim something is a theorem, show me the proof. If you claim something is experimentally verified, describe the experimental design and its results. What we have here is an appeal to authority claiming that the theory is "backed by math and logic" or that "physics would break" if it were untrue, omnes in verbo [all on the word (of authority)].
I would not be so demanding that I ask anyone to perform experiments, or even look up experimental data in literature, for the purpose of making a "Motte" post. A plausible (but concrete) story of what such evidence would look like -- in evidence of any theory of your choice -- would be enough to rebut my argument.
An appeal to authority is warranted here, rebutting your argument doesn't actually hinge on the truth of the theory, it hinges on whether it is possible for experimental evidence to justify a belief in the correspondence of a theory and reality. If it does there are cases where the logic of the theory enforces universality.
To wit, taking Newton's law as an example (and supposing we only knew classical mechanics), would we be justified in saying that the masses we observe behave as per his theory?
I'm not saying universally, merely the things we've observed locally.
If so, it turns out there are other cases, where if we are justified in believing the theory, the theory says things about the universe as a whole.
If you don't believe we can go from experimental evidence to justified belief in theory, then we have bigger problems.
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Well I’m a layman at physics, so I’d suggest finding someone who can lay out the math, theory, and experimentation that shows it is impossible for any object with mass to travel faster than the speed of light.
My layman’s understanding is that the fundamental properties of spacetime, mass, and energy as we understand them via Special Relativity make it impossible.
Here’s a bunch of physics nerds describing how it would violate causality:
https://physics.stackexchange.com/questions/671516/proof-for-impossibility-of-ftl-signals
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