Hypothetico-deductive model
Encyclopedia
The hypothetico-deductive model or method, first so-named by William Whewell
, is a proposed description of scientific method
. According to it, scientific inquiry proceeds by formulating a hypothesis
in a form that could conceivably be falsified by a test on observable data. A test that could and does run contrary to predictions of the hypothesis is taken as a falsification
of the hypothesis. A test that could but does not run contrary to the hypothesis corroborates the theory. It is then proposed to compare the explanatory value of competing hypotheses by testing how stringently they are corroborated by their predictions.
Qualification of corroborating evidence is sometimes raised as philosophically problematic. The raven paradox
is a famous example. The hypothesis that 'all ravens are black' would appear to be corroborated by observations of only black ravens. However, 'all ravens are black' is logically equivalent
to 'all non-black things are non-ravens' (this is the contraposition
form of the original implication). 'This is a green tree' is an observation of a non-black thing that is a non-raven and therefore corroborates 'all non-black things are non-ravens'. It appears to follow that the observation 'this is a green tree' is corroborating evidence for the hypothesis 'all ravens are black'. Attempted resolutions may distinguish:
Corroboration is related to the problem of induction
, which arises because a general case (a hypothesis) cannot be logically deduced from any series of specific observations. That is, any observation can be seen as corroboration of any hypothesis if the hypothesis is sufficiently restricted. The argument has also been taken as showing that both observations are theory-laden
, and thus it is not possible to make truly independent observations. One response is that a problem may be sufficiently narrowed (or axiomatized) as to take everything except the problem (or axiom) of interest as unproblematic for the purpose at hand.
Evidence contrary to a hypothesis is itself philosophically problematic. Such evidence is called a falsification
of the hypothesis. However, under the theory of confirmation holism
it is always possible to save a given hypothesis from falsification. This is so because any falsifying observation is embedded in a theoretical background, which can be modified in order to save the hypothesis. Popper acknowledged this but maintained that a critical approach respecting methodological rules that avoided such immunizing stratagems is conducive to the progress of science.
Despite the philosophical questions raised, the hypothetico-deductive model remains perhaps the best understood theory of scientific method.
This is an example of an algorithmic statement of the hypothetico-deductive method:
Types of inference
William Whewell
William Whewell was an English polymath, scientist, Anglican priest, philosopher, theologian, and historian of science. He was Master of Trinity College, Cambridge.-Life and career:Whewell was born in Lancaster...
, is a proposed description of scientific method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...
. According to it, scientific inquiry proceeds by formulating a hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
in a form that could conceivably be falsified by a test on observable data. A test that could and does run contrary to predictions of the hypothesis is taken as a falsification
Falsifiability
Falsifiability or refutability of an assertion, hypothesis or theory is the logical possibility that it can be contradicted by an observation or the outcome of a physical experiment...
of the hypothesis. A test that could but does not run contrary to the hypothesis corroborates the theory. It is then proposed to compare the explanatory value of competing hypotheses by testing how stringently they are corroborated by their predictions.
Qualification of corroborating evidence is sometimes raised as philosophically problematic. The raven paradox
Raven paradox
The Raven paradox, also known as Hempel's paradox or Hempel's ravens is a paradox proposed by the German logician Carl Gustav Hempel in the 1940s to illustrate a problem where inductive logic violates intuition...
is a famous example. The hypothesis that 'all ravens are black' would appear to be corroborated by observations of only black ravens. However, 'all ravens are black' is logically equivalent
Logical equivalence
In logic, statements p and q are logically equivalent if they have the same logical content.Syntactically, p and q are equivalent if each can be proved from the other...
to 'all non-black things are non-ravens' (this is the contraposition
Contraposition
In traditional logic, contraposition is a form of immediate inference in which from a given proposition another is inferred having for its subject the contradictory of the original predicate, and in some cases involving a change of quality . For its symbolic expression in modern logic see the rule...
form of the original implication). 'This is a green tree' is an observation of a non-black thing that is a non-raven and therefore corroborates 'all non-black things are non-ravens'. It appears to follow that the observation 'this is a green tree' is corroborating evidence for the hypothesis 'all ravens are black'. Attempted resolutions may distinguish:
- non-falsifying observations as to strong, moderate, or weak corroborations
- investigations that do or do not provide a potentially falsifying test of the hypothesis.
Corroboration is related to the problem of induction
Problem of induction
The problem of induction is the philosophical question of whether inductive reasoning leads to knowledge. That is, what is the justification for either:...
, which arises because a general case (a hypothesis) cannot be logically deduced from any series of specific observations. That is, any observation can be seen as corroboration of any hypothesis if the hypothesis is sufficiently restricted. The argument has also been taken as showing that both observations are theory-laden
Confirmation holism
Confirmation holism, also called epistemological holism is the claim that a single scientific theory cannot be tested in isolation; a test of one theory always depends on other theories and hypotheses....
, and thus it is not possible to make truly independent observations. One response is that a problem may be sufficiently narrowed (or axiomatized) as to take everything except the problem (or axiom) of interest as unproblematic for the purpose at hand.
Evidence contrary to a hypothesis is itself philosophically problematic. Such evidence is called a falsification
Falsifiability
Falsifiability or refutability of an assertion, hypothesis or theory is the logical possibility that it can be contradicted by an observation or the outcome of a physical experiment...
of the hypothesis. However, under the theory of confirmation holism
Confirmation holism
Confirmation holism, also called epistemological holism is the claim that a single scientific theory cannot be tested in isolation; a test of one theory always depends on other theories and hypotheses....
it is always possible to save a given hypothesis from falsification. This is so because any falsifying observation is embedded in a theoretical background, which can be modified in order to save the hypothesis. Popper acknowledged this but maintained that a critical approach respecting methodological rules that avoided such immunizing stratagems is conducive to the progress of science.
Despite the philosophical questions raised, the hypothetico-deductive model remains perhaps the best understood theory of scientific method.
This is an example of an algorithmic statement of the hypothetico-deductive method:
- Gather data (observations about something that is unknown, unexplained, or new)
- Hypothesize an explanation for those observations.
- Deduce a consequence of that explanation (a prediction). Formulate an experiment to see if the predicted consequence is observed.
- Wait for corroboration. If there is corroboration, go to step 3. If not, the hypothesis is falsified. Go to step 2.
Related subjects
- Confirmation biasConfirmation biasConfirmation bias is a tendency for people to favor information that confirms their preconceptions or hypotheses regardless of whether the information is true.David Perkins, a geneticist, coined the term "myside bias" referring to a preference for "my" side of an issue...
- Deductive-nomologicalDeductive-nomologicalThe deductive-nomological model is a formalized view of scientific explanation in natural language. It characterizes scientific explanations primarily as deductive arguments with at least one natural law statement among its premises...
- Explanandum and explanansExplanandumAn explanandum is a phenomenon that needs to be explained and its explanans is the explanation of that phenomenon. For example, one person may pose an explanandum by asking "Why is there smoke?", and another may provide an explanans by responding "Because there is a fire"...
- InquiryInquiryAn inquiry is any process that has the aim of augmenting knowledge, resolving doubt, or solving a problem. A theory of inquiry is an account of the various types of inquiry and a treatment of the ways that each type of inquiry achieves its aim.-Deduction:...
- Models of scientific inquiryModels of scientific inquiryIn the philosophy of science, models of scientific inquiry have two functions: first, to provide a descriptive account of how scientific inquiry is carried out in practice, and second, to provide an explanatory account of why scientific inquiry succeeds as well as it appears to do in arriving at...
- Philosophy of sciencePhilosophy of scienceThe philosophy of science is concerned with the assumptions, foundations, methods and implications of science. It is also concerned with the use and merit of science and sometimes overlaps metaphysics and epistemology by exploring whether scientific results are actually a study of truth...
- Scientific methodScientific methodScientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...
- Verifiability theory of meaning
- PragmatismPragmatismPragmatism is a philosophical tradition centered on the linking of practice and theory. It describes a process where theory is extracted from practice, and applied back to practice to form what is called intelligent practice...
- Will to Believe DoctrineWill to believe doctrine"The Will to Believe" is a lecture by William James, first published in 1896, which defends, in certain cases, the adoption of a belief without prior evidence of its truth...
Types of inference
- Strong inferenceStrong inferenceIn philosophy of science, strong inference is a model of scientific inquiry that emphasises the need for alternative hypotheses, rather than a single hypothesis in order to avoid confirmation bias....
- Abductive reasoningAbductive reasoningAbduction is a kind of logical inference described by Charles Sanders Peirce as "guessing". The term refers to the process of arriving at an explanatory hypothesis. Peirce said that to abduce a hypothetical explanation a from an observed surprising circumstance b is to surmise that a may be true...
- Deductive reasoningDeductive reasoningDeductive reasoning, also called deductive logic, is reasoning which constructs or evaluates deductive arguments. Deductive arguments are attempts to show that a conclusion necessarily follows from a set of premises or hypothesis...
- Inductive reasoningInductive reasoningInductive reasoning, also known as induction or inductive logic, is a kind of reasoning that constructs or evaluates propositions that are abstractions of observations. It is commonly construed as a form of reasoning that makes generalizations based on individual instances...
- AnalogyAnalogyAnalogy is a cognitive process of transferring information or meaning from a particular subject to another particular subject , and a linguistic expression corresponding to such a process...