As with all discussions it is useful to define the terminology at the outset, so that the discussion means the same thing to all the participants. The underpinnings of science are philosophical and can get to be partisan to various groups of philosophers. That is of little concern to scientists for the most part. Still, even amongst the science community there is variability as is seen in various text books that try to define science for the benefit of student readers.
Some of the more disingenuous definitions are these flip statements that I have actually seen published:
“Science is that which the majority of scientists say it is.”
“Science is whatever scientists do.”
Besides not being useful these statements obscure the fact that methods really are important to science and scientists. One of the best definitions is the one that Karl Popper develops in the first several chapters of his book, “The Logic of Scientific Discovery”. I’ll try to summarize without prejudicing his concept:
The scientific method is more than just inductive gathering of instances of a fact followed by an inference of natural law from those instances (forensics): there is a “problem of induction” to be considered shortly.
Verification science, or empiricism, has the following preliminary elements according to Popper: First, check the internal consistency of the proposal to be tested; second, test for the character of the proposal, whether it is empirically qualified or if it is tautological or other non-qualified nature; third, compare with other theories to determine if it would actually provide a scientific advancement; finally, test the theory by way of empirical applications of the conclusions which can be derived from it (deduction of consequences).
These preliminaries fit into an overall empirical scheme that might be described as follows, going beyond Popper's preliminaries:
a) speculation and coherence check, possibly with inductive input, resulting in the formulation of a proposed hypothesis;
b) deductive experimental design and implementation;
c) data analysis and congruity check against hypothesis expectations;
d) adjust hypothesis and experimental design, and repeat.
Also, Popper insisted that it is necessary that falsification of the hypothesis be possible. Falsification is the most necessary criteria, according to Popper, because it allows the demarcation “between physical science and metaphysical speculation”. Any concept that cannot be falsified is not verifiable with physical techniques, and is outside the realm of materialist science. As Popper says, “it must be possible for an empirical scientific system to be refuted by experience”.
Experiments and the replication of experiments cannot provide verification, it only provides instances of non-falsification. This is because singular statements cannot accumulate sufficiently to provide a universal statement (law). This is a failure of induction, where instance cannot prove the truth of the entirety. The exception to this is falsification where a singular statement deductively indicates falseness, which according to the principle of the excluded middle prevents the statement from being true.
Popper takes the following position on induction:
“Now in my view there is no such thing as induction. Thus inference to theories, from singular statements which are ‘verified by experience’ (whatever that may mean), is logically inadmissible.”This position is essentially fatal to forensic inferential extrapolations such as those in evolutionary theory.
The problem of induction.
Induction has been addressed by a great many philosophers of science, from Hume on. There are several objections to induction.
First, there is the problem of verifying induction itself. If induction is a valid process for producing valid results, it should be able to verify itself. But it can’t verify itself if it is not known to be valid in advance. Further, if the principle of induction is taken as a universal, then the idea of validating the validator becomes an infinite regress, never resolving to a verification at any level. So the principle of induction cannot be verified, and cannot be a universal.
Next, according to Schlick (per Popper), “The problem of induction consists in asking for a logical justification of universal statements about reality… we recognize, with Hume, that there is no such logical justification: there can be none, simply because they are not genuine statements.” Hume had said that no amount of “constant conjunction” between events could ever prove the conjunction to be a universal (or law). For instance, if every object we encounter is red, it does not follow that the next object we encounter should be red. As Popper shows, the probability does not approach 1 without becoming a tautology.
Popper takes this one step more. Because induction cannot provide a demarcation between scientific and metaphysical systems, then statements about both systems are meaningless (being undifferentiable as well as non-falsifiable); thus while attempting to eliminate metaphysics from the empirical sciences, metaphysics is allowed (by induction) to invade the scientific realm, producing a contradictory or paradoxical result.
The Problem of Empiricism
Because in experimental science a single successful experiment provides a only a single instance of non-falsification, the need for more instances (replications) exists; this is an inductive accumulation, so the problem of inductive non-verifiability also applies. For this reason even empiricism cannot ever produce incorrigible, incontrovertible, noncontingent proof, in the sense of Truth. Truth is an object in metaphysics, and only metaphysics, never in science.
But empiricism also cannot verify “experiential” or “existential” statements. This is shown by the statement, “there are no white ravens”. No amount of either induction or deductive experimentation can bring a conclusive answer to such an assertion.
1. As Hume demonstrates, it is not possible to “demonstrate that the course of nature must continue uniformly the same… Nay, I will go farther, and assert that he could not so much as prove by any probable arguments that the future must be conformable to the past. All probable arguments are built on the supposition that there is conformity betwixt the future and the past, and therefore can never prove it”. (Hume; A Treatise of Human Nature)
For this reason is it axiomatic for science to presume conformity of the past within itself, and between the past and the future.
There are presumed to be no singularities, ever, that are variations in the physical laws. Since this cannot be proved, it is accepted as axiomatic.
2. Notwithstanding Hume’s denial of “constant conjunction” verifiability, the principle of cause and effect is accepted as axiomatic.
3. All the first principles of logic are accepted as axiomatic.
So the scientific method, even if restricted to experimental empiricism, is limited to physical objects that are measurable in the sense that they possess mass/energy and exist in space/time. The scientific method is limited by its inability to prove its basic assumptions (axioms) and is not axiomatic itself, and is not itself a universal. The scientific method cannot provide or argue for or against Truth, because Truth is a metaphysic and is outside the realm of the physical. The scientific method cannot prove existential statements, because of the limitations of the inductive method, inherent even in empiricism.
Commentaries on the Scientific Method
The following comments on the subject of the scientific method and the scientific attitude are taken from known, accomplished and respected scientists.
From Albert Einstein:
“For the scientific method can teach us nothing else beyond how facts are related to, and conditioned by, each other. The aspiration toward such objective knowledge belongs to the highest of which man is capable, and you will certainly not suspect me of wishing to belittle the achievements and the heroic effort of man in the sphere. Yet it is equally clear that knowledge of what is does not open the door directly to what should be. One can have the clearest and most complete knowledge of what is, and yet not be able to deduct from that what should be the goal of our human aspirations. Objective knowledge provides us with powerful instruments for the achievements of certain ends, but the ultimate goal itself and the longing to reach it must come from another source. And it is hardly necessary to argue for the view that our existence and our activity acquire meaning only by the setting up of such a goal and of corresponding values. The knowledge of truth as such is wonderful, but it is so little capable of acting as a guide that it cannot prove even the justification and the value of the aspiration towards that very knowledge of truth. Here we face, therefore the limits of the purely rational conception of our existence.”
“But it must not be assumed that intelligent thinking can play no part in the formation of the goal and of ethical judgments. When someone realizes that for the achievement of an end certain means would be useful, the means itself thereby becomes and end. Intelligence makes clear to us the interrelation of means and ends. But mere thinking cannot give us a sense of the ultimate and fundamental ends. To make clear these fundamental ends and valuations, and to set them fast in the emotional life of the individual, seems to me precisely the most important function which religion has to perform in the social life of man. And if one asks whence derives the authority of such fundamental ends, since they cannot be stated and justified merely by reason, one can only answer: they exist in a healthy society as powerful traditions, which act upon the conduct and aspirations and judgments of the individuals; they are there that is, as something living, without its being necessary to find justification for their existence. They come into being not through demonstration but through revelation, through the medium of powerful personalities. One must not attempt to justify them, but rather to sense their nature simply and clearly.“ The highest principles for our aspirations and judgments are given to us in the Jewish-Christian religious tradition.”
Albert Einstein; “Out Of My Later Years”; Wing Books, Random House; copyright 1956, written in 1950, revised in 1956; pg 20,21.
Also from Einstein:
“The supreme task of the physicist is to search for those highly universal laws…from which a picture of the world can be obtained by pure deduction. There is no logical path leading to these…laws. They can only be reached by intuition, based upon something like an intellectual love of the objects of experience.”
Albert Einstein; speech on the 60th birthday of Max Plank, 1918; from “The World As I See It”, 1935.
Attributed to Feynman:
“It's a kind of scientific integrity, a principle of scientific thought that corresponds to a kind of utter honesty--a kind of leaning over backwards. For example, if you're doing an experiment, you should report everything that you think might make it invalid--not only what you think is right about it: other causes that could possibly explain your results; and things you thought of that you've eliminated by some other experiment, and how they worked--to make sure the other fellow can tell they have been eliminated.
“Details that could throw doubt on your interpretation must be given, if you know them. You must do the best you can--if you know anything at all wrong, or possibly wrong--to explain it. If you make a theory, for example, and advertise it, or put it out, then you must also put down all the facts that disagree with it, as well as those that agree with it. There is also a more subtle problem. When you have put a lot of ideas together to make an elaborate theory, you want to make sure, when explaining what it fits, that those things it fits are not just the things that gave you the idea for the theory; but that the finished theory makes something else come out right, in addition.
“Remember: In science, we don't prove things true, we show them to be not false. Same thing? Not hardly. For a complete discussion on the topic, read the Logic of Scientific Discovery by Karl Popper. However what it comes down to is you do not do a test, and then prove a theory true. That can't be done. What you do is come up with a way to falsify your theory, that is to say you come up with a test that says "If things don't come out this way, we know this theory is wrong." You run the test, things come out that way. You have failed to falsify the theory, and we are now more certain it is true. The more than is done, the more certain we are a theory is correct. Each time we attempt to falsify the theory and fail, we are more sure it must be the truth.
“If we do then falsify it, the theory has to be redone. That doesn't mean you toss the whole thing out, it may just mean some refinement is needed. For example you have a theory that predicts when X happens Y will results. In 400 tests, this is the case, however 3 new tests show it isn't. What you discover is that in all those tests, A was also present. You the refine your theory: Y will result from X, except in cases where A is present. Your theory is now a little more narrow in application, and fits with the evidence. Perhaps later you find out what A does, and incorporate that in to a more general theory.
“The point of all this is that real science is all about trying to prove your theory wrong. You do everything you can to prove it wrong, then have other people do what they can to prove it wrong. When all of you fail at doing that, when the theory has been refined such that it fits all the evidence and you can't figure out how else to test it, then it is most likely the truth. THAT is what scientific rigor is about. It isn't about coming up with a theory, ignoring data you don't like, showing it to a few people who agree with you, and saying "Ok, we proved this true and nobody else can look at it."
And, from Feynman’s “Cargo Cult Science”:
“That is the idea that we all hope you have learned in studying
science in school--we never explicitly say what this is, but just
hope that you catch on by all the examples of scientific
investigation. It is interesting, therefore, to bring it out now
and speak of it explicitly. It's a kind of scientific integrity,
a principle of scientific thought that corresponds to a kind of
utter honesty--a kind of leaning over backwards. For example, if
you're doing an experiment, you should report everything that you
think might make it invalid--not only what you think is right about
it: other causes that could possibly explain your results; and
things you thought of that you've eliminated by some other
experiment, and how they worked--to make sure the other fellow can
tell they have been eliminated.
“Details that could throw doubt on your interpretation must be
given, if you know them. You must do the best you can--if you know
anything at all wrong, or possibly wrong--to explain it. If you
make a theory, for example, and advertise it, or put it out, then
you must also put down all the facts that disagree with it, as well
as those that agree with it. There is also a more subtle problem.
When you have put a lot of ideas together to make an elaborate
theory, you want to make sure, when explaining what it fits, that
those things it fits are not just the things that gave you the idea
for the theory; but that the finished theory makes something else
come out right, in addition.
“In summary, the idea is to try to give all of the information to
help others to judge the value of your contribution; not just the
information that leads to judgment in one particular direction or
“The easiest way to explain this idea is to contrast it, for
example, with advertising. Last night I heard that Wesson oil
doesn't soak through food. Well, that's true. It's not dishonest;
but the thing I'm talking about is not just a matter of not being
dishonest, it's a matter of scientific integrity, which is another
level. The fact that should be added to that advertising statement
is that no oils soak through food, if operated at a certain
temperature. If operated at another temperature, they all will--
including Wesson oil. So it's the implication which has been
conveyed, not the fact, which is true, and the difference is what
we have to deal with.
“We've learned from experience that the truth will come out. Other
experimenters will repeat your experiment and find out whether you
were wrong or right. Nature's phenomena will agree or they'll
disagree with your theory. And, although you may gain some
temporary fame and excitement, you will not gain a good reputation
as a scientist if you haven't tried to be very careful in this kind
of work. And it's this type of integrity, this kind of care not to
fool yourself, that is missing to a large extent in much of the
research in cargo cult science.
“A great deal of their difficulty is, of course, the difficulty of
the subject and the inapplicability of the scientific method to the
subject. Nevertheless it should be remarked that this is not the
only difficulty. That's why the planes didn't land--but they don't
From Karl Popper’s “Logic of Scientific Discovery”:
“The old scientific ideal of episteme - of absolutely certain, demonstrable knowledge – has proved to be an idol. The demand for scientific objectivity makes it inevitable that every scientific statement must remain tentative forever. It may indeed be corroborated, but every corroboration is relative to other statements which, again, are tentative. Only in our subjective experiences of conviction, in our subjective faith, can we be ‘absolutely certain’.
“With the idol of certainty (including that of degrees of imperfect certainty or probability) there falls one of the defences of obscurantism which bar the way for scientific advance. For the worship of this idol hampers not only the boldness of our questions, but also the rigour and the integrity of our tests. The wrong view of science betrays itself in the craving to be right; for it is not his possession of knowledge, of irrefutable truth, that makes the man of science, but his persistent and recklessly critical quest for truth.
“Has our attitude, then, to be one of resignation? Have we to say that science can fulfil only its biological task; that it can, at best, merely prove its mettle in practical applications which may corroborate it? I do not think so. Science never pursues the illusory aim of making its answers final, or even probable. Its advance is, rather, towards an infinite yet attainable aim: that of ever discovering new, deeper, and more general problems, and of subjection our ever tentative answers to ever renewed and ever more rigorous tests.
Popper, “The Logic of Scientific Discovery”, 1935, 2002, Routledge, p 280. [emphasis added]