Bold hypothesis (or bold conjecture, the terms are used interchangeably) is a concept originally created by the liberal philosopher Karl Popper when he tried to define the meaning of scientific thinking and scientific progress. It was first explained in his debut The Logic of Scientific Discovery (1935) and subsequently elaborated in writings such as Conjectures and Refutations: The Growth of Scientific Knowledge (1963), Objective knowledge: an evolutionary approach (1972), [1] and Replies to my critics (1974). [2] In successive texts written in the course of four decades, Popper added some nuances to the definition of the concept.
Broadly speaking, the idea of a bold hypothesis refers to a testable new proposal (or theoretical claim) made within a subject area which, if it is true, would be able to explain and predict much more about the subject than was previously possible. It would significantly alter existing scientific understandings about the subject, in a positive way. The new idea would be very useful for scientific research about the subject. This contrasts with other types of scientific claims which, if they turn out to be true, make little difference to what scientists already know about the subject. The contrary of a bold hypothesis is an "ad hoc hypothesis" which protects an well-established scientific theory from refutation, by means of some convenient modification of this theory which has no new testable consequences. [3]
The idea of a "bold hypothesis" is nowadays widely used in the philosophy of science and in the philosophy of knowledge. It is also used in the social, historical and physical sciences, to refer to significant new ways to understand something. Bold hypotheses are often understood to be an important ingredient of major scientific progress and scientific innovation. They can help to move scientific understanding forward. That is also why bold hypotheses have an important place in Karl Popper's theory of scientific progress.
However, when bold hypotheses are formulated, they don't necessarily meet all the scientific criteria required to test them yet. And not all of them survive the scientific tests that are eventually done. Some hypotheses stand up to the evidence, while others do not. Testing a bold hypothesis conclusively can be difficult. It can sometimes take a long time, before a bold hypothesis is definitely accepted or rejected. There are also bold hypotheses which, although they were ultimately rejected after relevant tests, nevertheless triggered a lot of new and valuable ideas about what might (or might not) be the case. They might help to rule out a lot of possibilities, and focus the research with new leads. Sometimes it is helpful to know what cannot be true, in order to find out what is true. [4]
Karl Popper's argument was that scientific progress occurs through formulating bold hypotheses, and trying to refute (disprove or falsify) them. Popper believed that:
"The advance of science is not due to the fact that more and more perceptual experiences accumulate in the course of time. Nor is it due to the fact that we are making ever better use of our senses. Out of uninterpreted sense-experiences science cannot be distilled, no matter how industriously we gather and sort them. Bold ideas, unjustified anticipations, and speculative thought, are our only means for interpreting nature: our only organon, our only instrument, for grasping her. And we must hazard them to win our prize. Those among us who are unwilling to expose their ideas to the hazard of refutation do not take part in the scientific game." [5]
He makes this point more specific in a 1953 lecture, where he argues that, if we aim to explain the world, then:
"... there is no more rational procedure than the method of trial and error – of conjecture and refutation: of boldly proposing theories; of trying our best to show that these are erroneous; and of accepting them tentatively if our critical efforts are unsuccessful. From the point of view here developed, all laws, all theories, remain essentially tentative, or conjectural, or hypothetical, even when we feel unable to doubt them any longer." [6]
In his 1974 reply to critics, Popper described the concept of bold hypotheses some more:
“Bold ideas are new, daring, hypotheses or conjectures. And severe attempts at refutations are severe critical discussions and severe empirical tests. When is a conjecture daring and when is it not daring, in the sense here proposed? Answer: it is daring if and only if it takes a great risk of being false – if matters could be otherwise, and seem at the time to be otherwise.” [7]
He added that the characteristic of bold conjectures, in combination with tests and refutations, is what distinguishes science from non-science, from prescientific myths and from metaphysics:
”There is a reality behind the world as it appears to us, possibly an many-layered reality, of which the appearances are the outermost layers. What the great scientist does is boldly to guess, daringly to conjecture, what these inner realities are like. (…) The boldness can be gauged by the distance between the world of appearance and the conjectured reality, the explanatory hypotheses. But there is another, a special kind of boldness – the boldness of predicting aspects of the world of appearance which so far have been overlooked but which it must possess if the conjectured reality is (more or less) right, if the explanatory hypotheses are (approximately) true. It is this more special kind of boldness which I have usually in mind when I speak of bold scientific conjectures. It is the boldness of a conjecture which takes a real risk – the risk of being tested and refuted; the risk of clashing with reality. Thus my proposal was, and is, that it is this second boldness, together with the readiness to look out for tests and refutations, which distinguishes “empirical” science from nonscience, and especially from prescientific myths and metaphysics.” [8]
This passage makes it very clear, that the idea of bold hypotheses has a central role in Popper's solution for the demarcation problem, i.e. the problem of how scientific knowledge and scientific practice can be distinguished from non-scientific beliefs and practices.
A "bold" hypothesis is a new scientific idea which, if it was true, would be able to predict and/or explain a lot, or a lot more, about the subject being theorized about. The "boldness" of a scientific hypothesis can be evaluated with the following criteria:
Once a bold hypothesis has been mooted, Popper argues, scientists try to investigate and test how well the bold hypothesis can stand up to the known evidence. They try to find counter-arguments that would refute or falsify the bold hypothesis. In this process of testing and criticism, new scientific knowledge is generated. Even if the bold hypothesis turns out to have been wrong, testing it may well generate useful knowledge about what can and cannot be the case. Often it stimulates new research.
Inversely, if a hypothesis lacks the quality of boldness, then it would make very little difference to what scientists already know. It is not "a big deal", i.e. it is not very significant for the knowledge which exists already. It contributes little to advancing scientific progress, because it does not expand or add anything much to scientific understanding.
According to Popper,
"Science does not rest upon solid bedrock. The bold structure of its theories rises, as it were, above a swamp. It is like a building erected on piles. The piles are driven down from above into the swamp, but not down to any natural or ‘given’ base; and if we stop driving the piles deeper, it is not because we have reached firm ground. We simply stop when we are satisfied that the piles are firm enough to carry the structure, at least for the time being." " [13]
In one of his later writings, Objective Knowledge (1972), Popper argued that:
"A theory is the bolder the greater its content. It is also the riskier: it is the more probable to start with that it will be false. We try to find its weak points, to refute it. If we fail to refute it, or if the refutations we find are at the same time also refutations of the weaker theory which was its predecessor, then we have reason to suspect, or to conjecture, that the stronger theory has no greater falsity content than its weaker predecessor, and, therefore, that it has the greater degree of verisimilitude". [14]
This interpretation was criticized by Adolf Grünbaum. [15]
Alan F. Chalmers summarizes that in Popper's philosophy of science,
"A very good theory will be one that makes very wideranging claims about the world, and which is consequently highly falsifiable, and is one that resists falsification whenever it is put to the test." [16]
Popper's idea of the role of bold hypotheses in scientific progress has attracted four main kinds of criticisms. These concern (1) the meaning of "boldness", (2) the issue of testability, (3) the issue of falsifiability, and (4) the realities of normal science.
The idea of a bold hypothesis is itself somewhat fuzzy, because exactly "how bold is bold"? Is boldness always a good thing in hypothesizing? [17] It might just depend on how you care to look at it.
So it remains somewhat fuzzy what kinds of criteria or relativizations we might use, to credit new hypotheses as "bold" or not. There could be an element of propaganda in the "boldness".
In Popper's philosophy of science, scientific statements are always provisional, they have limits of application, and they could always be wrong. If a statement cannot even in principle be proved wrong, it cannot be a scientific statement. Thus, in Popper's eyes, the falsifiability criterion clearly demarcates "science" from "non-science". This Popperian idea has been very controversial, however. The reason is that it can be quite difficult to test scientifically how true a particular idea is. Even if scientists do want to test an idea, they may not know yet how exactly to test it conclusively. Yet, scientists also don't want to abandon a hunch that seems useful, simply because they don't know how to verify it yet. This point is especially important for "bold" new hypotheses, because the very "boldness" of the new hypothesis could mean that it would take a lot of work before adequate tests could be designed and carried out.
Some philosophers have argued that, in the real world, scientists operate routinely with at least some metaphysical beliefs for which they have no proof or verification whatsoever. [19] In fact, in The logic of scientific discovery, Karl Popper admits that this is the case:
“I do not… go so far as to assert that metaphysics has no value for empirical science. (…) looking at the matter from the psychological angle, I am inclined to think that scientific discovery is impossible without faith in ideas which are of a purely speculative kind, and sometimes even quite hazy; a faith which is completely unwarranted from the point of view of science, and which, to that extent, is ‘metaphysical’.” [20]
Nevertheless Popper considered it his task to formulate a logical model of the method of empirical science, in which psychological factors or speculative/metaphysical thought play no role.
According to Paul Feyerabend, the creative processes that lead to a scientific discovery are usually quite reasonable and non-arbitrary. However, the creative processes are by no means fully "rational", and they can be quite unique. Therefore, he argued, the idea that there is one standard model which can define the rationality of all scientific methods should be rejected. [21] This contrasts with Karl Popper's view that "Just as chess might be defined by the rules proper to it, so empirical science may be defined by means of its methodological rules". [22]
The philosopher Imre Lakatos argued (against Karl Popper's interpretation) that scientists do not aim to test bold hypotheses in order to falsify them; instead, they aim mainly to confirm hypotheses. [23]
Thomas Kuhn argued that Popper's interpretation does not provide a very realistic picture of what most scientists actually do, most of the time. [26] He argued that Popper focused on the “glamorous” side of scientific work in the "revolutionary" episodes of a science, when old solutions are questioned and are not effective anymore, and radically new approaches are being tried out. In Popper's own words, “It is the working of great scientists that I have in my mind as my paradigm for science”. [27] In much, if not most, scientific work in the real world, Kuhn claims, scientists are not mooting bold hypotheses that could overturn established views. Instead, they are working patiently on systematic, detailed tests of a small facet of a much larger theory or research paradigm; Kuhn called this practice "normal science". Thus, scientific progress may come about, not because somebody has a grandiose new idea, but instead because the careful testing of the details of a theory eventually provides definitive scientific conclusions that are generally accepted.
Despite these important criticisms, Popper's concept of bold hypotheses continues to be widely used in the academic world. One reason is that, at some level, the concept does make sense, even if (arguably) Popper himself failed to define its role in scientific research very well. Another reason is that academic progress always requires that a scholar does something genuinely new and "breaks new ground". If a scholar only concerns themself with tiny, uncontroversial and fairly trivial claims, they are unlikely to be rewarded very much for their effort. Plausible and credible bold hypotheses are highly valued in the academic world, so long as they are reasonably consistent with (or cohere with) well-established scientific findings, and do not seriously challenge scientific authority.
In the business community, too, innovation is very important, to find new ways to reduce costs, increase productivity and sales, and raise profits. [28] A bold new idea can be worth a lot of money, and therefore, business people are often sympathetic to bold attempts to reframe what is known already and to create new ideas; without such innovations, they would eventually be defeated by competitors who have a better idea. So the idea of a bold hypothesis also continues to have a place in economics, management theory and business administration.