A working hypothesis is a hypothesis that is provisionally accepted as a basis for further research in the hope that a tenable theory will be produced, even if the hypothesis ultimately fails. Like all hypotheses, a working hypothesis is constructed as a statement of expectations, which can be linked to the exploratory research  purpose in empirical investigation and is often used as a conceptual framework in qualitative research.
Use of the phrase "working hypothesis" goes back at least two centuries.
Charles Sanders Peirce came to hold that an explanatory hypothesis is not only justifiable as a tentative conclusion by its plausibility (by which he meant its naturalness and economy of explanation), but also justifiable as a starting point by the broader promise that the hypothesis holds for research. This idea of justifying a hypothesis as potentially fruitful (at the level of research method), not merely as plausible (at the level of logical conclusions), is essential for the idea of a working hypothesis, as later elaborated by Peirce's fellow pragmatist John Dewey.
Peirce held that, as a matter of research method, an explanatory hypothesis is judged and selected for research because it offers to economize and expedite the process of inquiry, by being testable and by further factors in the economy of hypotheses: low cost, intrinsic value (instinctive naturalness and reasoned likelihood), and relations (caution, breadth, and incomplexity) among hypotheses, inquiries, etc. (as in the game of Twenty Questions). The Century Dictionary Supplement definition of "working hypothesis" reflects that perspective; Peirce may or may not have written it. Peirce seldom used the phrase "working hypothesis," but he once commented about a related kind of a hypothesis that it was "a hypothesis, which like the working hypothesis of a scientific inquiry, we may not believe to be altogether true, but which is useful in enabling us to conceive of what takes place." For Peirce the pragmatist, conceiving pragmatically of something meant conceiving of its effects in their conceivable implications as to informed practice in general including research.
John Dewey used the concept of the working hypothesis as a pivotal feature in his theory of inquiry. Contrary to the principles of verification and falsifiability, used in formal hypothesis testing found within dominant paradigms of 'normal' science, working hypotheses were conceived by Dewey as neither true nor false but "provisional, working means of advancing investigation," which lead to the discovery of other unforeseen but "relevant" facts. Dewey's development of the concept of the working hypothesis emerged from his contextualist epistemology in which absolute truth is unobtainable and replaced by "warranted assertability". Thus, Dewey noted:
The history of science also shows that when hypotheses have been taken to be finally true and hence unquestionable, they have obstructed inquiry and kept science committed to doctrines that later turned out to be invalid.
In Dewey's view, the working hypothesis is generated, not directly as a testable statement of, but instead in order to "direct inquiry into channels in which new material, factual and conceptual, is disclosed, material which is more relevant, more weighted and confirmed, more fruitful, than were the initial facts and conceptions which served as the point of departure".
Working hypotheses are constructed to facilitate inquiry; however, formal hypotheses can often be constructed based on the results of the inquiry, which in turn allows for the design of specific experiments whose data will either support or fail to support the formal hypotheses. In Unity of Science as a Working Hypothesis Oppenheim and Putnam argued that unitary science, in which laws from one branch could be equally useful by others, could only be accepted tentatively without further empirical testing. Thus they argued:
We therefore think the assumption that unitary science can be attained through cumulative micro-reduction recommends itself as a working hypothesis. That is, we believe that it is in accord with the standards of reasonable scientific judgment to tentatively accept this hypothesis and to work on the assumption that further progress can be made in this direction.
For Putnam, the working hypothesis, therefore, represents a practical starting point in the design of an empirical research exploration. A contrasting example of this conception of the working hypothesis is illustrated by the brain-in-a-vat thought experiment. This experiment involves confronting the global skeptic position that we, in fact, are all just brains in vats being stimulated by a mad scientist to believe that our reality is real. Putnam argued that this proposition, however, rests on a "magical theory of reference" in which the existential evidence necessary to validate it is assumed. Thus, the brain-in-a-vat proposition does not make for much of a hypothesis at all since there is no means to verify its truth. It does, however, provide a contrast for what a good working hypothesis would look like: one suited to culling potential existential evidence of the subject at hand.
A more concrete example would be that of conjectures in mathematics – propositions which appear to be true but which are formally unproven. Very often, conjectures will be provisionally accepted as working hypotheses in order to investigate its consequences and formulate conditional proofs.
In the field of public administration working hypotheses are used as a conceptual framework for exploratory, applied, empirical research  Research projects that use working hypotheses use a deductive reasoning or logic of inquiry. In other words, the problem and preliminary theory are developed ahead of time and tested using evidence. Working hypotheses (statements of expectation) are flexible and incorporate relational or non-relational statements. They are often used as ways to investigate a problem in a particular city or public agency. These projects are a type of case study and use multiple methods of evidence collection. The working hypotheses are used as a device to direct evidence collection. As a result, working hypotheses are generally organized using sub-hypotheses, which specify in more detail the kinds of data or evidence needed to support the hypothesis.
hypothesis [...]—Working hypothesis, a hypothesis suggested or supported in some measure by features of observed facts, from which consequences may be deduced which can be tested by experiment and special observations, and which it is proposed to subject to an extended course of such investigation, with the hope that, even should the hypothesis thus be overthrown, such research may lead to a tenable theory.
Methodeutic has a special interest in Abduction, or the inference which starts a scientific hypothesis. For it is not sufficient that a hypothesis should be a justifiable one. Any hypothesis which explains the facts is justified critically. But among justifiable hypotheses we have to select that one which is suitable for being tested , experiment.
Consequently, to discover is simply to expedite an event that would occur sooner or later, if we had not troubled ourselves to make the discovery. Consequently, the art of discovery is purely a question of economics. The economics of research is, so far as logic is concerned, the leading doctrine with reference to the art of discovery. Consequently, the conduct of abduction, which is chiefly a question of heuretic and is the first question of heuretic, is to be governed by economical considerations.