The hypothetico-deductive model or method is a proposed description of the

scientific method The scientific method is an empirical method for acquiring knowledge that has characterized the development of science since at least the 17th century (with notable practitioners in previous centuries; see the article history of scientific m ...

. According to it,

scientific inquiry 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 ap ...

proceeds by formulating a

hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...

in a form that can be

falsifiable Falsifiability is a standard of evaluation of scientific theories and hypotheses that was introduced by the philosopher of science Karl Popper in his book ''The Logic of Scientific Discovery'' (1934). He proposed it as the cornerstone of a sol ...

, using a test on observable data where the outcome is not yet known. A test outcome that could have and does run contrary to predictions of the hypothesis is taken as a falsification of the hypothesis. A test outcome that could have, 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.

Example

One example of an algorithmic statement of the hypothetico-deductive method is as follows:

:''1''. Use your experience: Consider the problem and try to make sense of it. Gather data and look for previous explanations. If this is a new problem to you, then move to step ''2''. :''2''. Form a conjecture (

): When nothing else is yet known, try to state an explanation, to someone else, or to your notebook. :''3''. Deduce predictions from the hypothesis: if you assume ''2'' is true, what consequences follow? :''4''. Test (or

experiment An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into Causality, cause-and-effect by demonstrating what outcome oc ...

): Look for evidence (observations) that conflict with these predictions in order to disprove ''2''. It is a logical error to seek ''3'' directly as proof of ''2''. This

formal fallacy In philosophy, a formal fallacy, deductive fallacy, logical fallacy or non sequitur (; Latin for " tdoes not follow") is a pattern of reasoning rendered invalid by a flaw in its logical structure that can neatly be expressed in a standard logic syst ...

is called '' affirming the consequent''.

One possible sequence in this model would be ''1'', ''2'', ''3'', ''4''. If the outcome of ''4'' holds, and ''3'' is not yet disproven, you may continue with ''3'', ''4'', ''1'', and so forth; but if the outcome of ''4'' shows ''3'' to be false, you will have to go back to ''2'' and try to invent a ''new 2'', deduce a ''new 3'', look for ''4'', and so forth. Note that this method can never absolutely verify (prove the truth of) ''2''. It can only

falsify Falsifiability is a standard of evaluation of scientific theories and hypotheses that was introduced by the philosopher of science Karl Popper in his book ''The Logic of Scientific Discovery'' (1934). He proposed it as the cornerstone of a sol ...

''2''. (This is what Einstein meant when he said, "No amount of experimentation can ever prove me right; a single experiment can prove me wrong.")

Discussion

Additionally, as pointed out by

Carl Hempel Carl Gustav "Peter" Hempel (January 8, 1905 – November 9, 1997) was a German writer, philosopher, logician, and epistemologist. He was a major figure in logical empiricism, a 20th-century movement in the philosophy of science. He is espec ...

(1905–1997), this simple view of the scientific method is incomplete; a conjecture can also incorporate probabilities, e.g., the drug is effective about 70% of the time. Tests, in this case, must be repeated to substantiate the conjecture (in particular, the probabilities). In this and other cases, we can quantify a probability for our confidence in the conjecture itself and then apply a Bayesian analysis, with each experimental result shifting the probability either up or down.

Bayes' theorem In probability theory and statistics, Bayes' theorem (alternatively Bayes' law or Bayes' rule), named after Thomas Bayes, describes the probability of an event, based on prior knowledge of conditions that might be related to the event. For examp ...

shows that the probability will never reach exactly 0 or 100% (no absolute certainty in either direction), but it can still get very close to either extreme. See also

confirmation holism In philosophy of science, confirmation holism, also called epistemological holism, is the view that no individual statement can be confirmed or disconfirmed by an empirical test, but rather that only a set of statements (a whole theory) can be so. ...

. Qualification of corroborating evidence is sometimes raised as philosophically problematic. The

raven paradox The raven paradox, also known as Hempel's paradox, Hempel's ravens, or rarely the paradox of indoor ornithology, is a paradox arising from the question of what constitutes evidence for the truth of a statement. Observing objects that are neither ...

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

contrapositive In logic and mathematics, contraposition refers to the inference of going from a conditional statement into its logically equivalent contrapositive, and an associated proof method known as proof by contraposition. The contrapositive of a statemen ...

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. Evidence contrary to a hypothesis is itself philosophically problematic. Such evidence is called a falsification of the hypothesis. However, under the theory of

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.

Karl Popper Sir Karl Raimund Popper (28 July 1902 – 17 September 1994) was an Austrian-British philosopher, academic and social commentator. One of the 20th century's most influential philosophers of science, Popper is known for his rejection of the cl ...

acknowledged this but maintained that a critical approach respecting methodological rules that avoided such ''immunizing stratagems'' is conducive to the progress of science. Physicist Sean Carroll claims the model ignores underdetermination. The hypothetico-deductive model (or approach) versus other research models The hypothetico-deductive approach contrasts with other research models such as the inductive approach or grounded theory. In the data percolation methodology, the hypothetico-deductive approach is included in a paradigm of pragmatism by which four types of relations between the variables can exist: descriptive, of influence, longitudinal or causal. The variables are classified in two groups, structural and functional, a classification that drives the formulation of hypotheses and the statistical tests to be performed on the data so as to increase the efficiency of the research.

Citations

References

* . (

Luis de la Peña Luis Fernando de la Peña-Auerbach known as Luis de la Peña is a Mexican physicist, born in Mexico City in 1931. He is a researcher of the Institute of Physics and professor of the Faculty of Sciences of the National Autonomous University of M ...

and Peter E. Hodgson, eds.) * . * * {{DEFAULTSORT:Hypothetico-Deductive Model Scientific method Philosophy of science Conceptual models

Example

Discussion

See also

Types of inference

Citations

References