Scientific method

Table of contents

1 History 2 The scientific method 2.1 Characterization 2.2 Develop an Hypothesis 2.3 Prediction from the hypothesis 2.4 Experiment 2.5 Evaluation and iteration 2.5.1 Testing and improvement 2.5.2 Verification 2.5.2.1 Peer review evaluation 2.5.2.2 Reproducibility 2.5.3 Reevaluation 2.5.4 Evidence and assumptions 2.5.5 Elegance of hypothesis 3 Philosophical issues 3.6 Theory-dependence of observation 3.7 Indeterminacy of theory under empirical test 3.8 Demarcation 3.9 Science as a communal activity 4 Scientific method and the practice of science 5 Annotated list of related issues 6 External links

History

In his enunciation of a 'method' in the thirteenth century, Roger Bacon was inspired by the writings of Arab alchemists, who had preserved and built upon Aristotle's portrait of induction. Bacon described a repeating cycle of observation, hypothesis, experimentation, and the need for independent verification. In the 17th century Francis Bacon attempted to describe a rational procedure for establishing causation between phenomena.

Galileo Galilei introduced quantitative experimentation and mathematical analysis, which permitted the enunciation of general physical laws. Isaac Newton systematised these laws, becoming a model which other sciences sort to emulate.

Attempts to systematise the scientific method were faced with the Problem of induction, which points out that inductive reasoning is not logically valid. David Hume set the difficulty out in detail. Karl Popper, following others, argued that a hypothesis must be falsifiable; that is, it must be capable of disproof. Difficulties with this have led to the rejection of the very idea that there is a single method that is universally applicable to all the sciences, and that serves to distinguish science from non-science.

The question of how science operates has importance well beyond scientific circles or the academic community. In the judicial system and in public policy controversies, for example, a study's deviation from accepted scientific practice is grounds for rejecting it as "junk science" or pseudoscience.

The scientific method

The essential elements of the scientific method are iterations and recursions of the following four steps:

1. Characterization
2. Hypothesis (a theoretical, hypothetical explanation)
3. Prediction (logical deduction from the hypothesis)
4. Experiment (test of all of the above)

Science is a social activity. The process is subject to evaluation by the scientists directly involved, or by the scientific community, at any or every stage. A scientist's theory or proposal is accepted only after it has become known to others (usually via publication, ideally peer reviewed publication) and criticised. See the list of unsolved problems in science, for example.

Characterization

The scientific method depends upon the careful characterization of the subject of the investigation.

Observation demands careful measurement and the use of Operational definitions of relevant concepts. When the terms used are formally defining, they acquire exact meanings which do not necessarily correspond with their use in natural language: for example, mass and weight are quite distinct concepts, but the distinction is often ignored in everyday life.

New theories may arise when it is realised that words used have not previously been clearly defined. For example, Albert Einstein's first paper on relativity begins by defining simultaneity and the means for determining length (which were skipped over by Isaac Newton with "I do not define time, space, place and motion, as being well known to all") and proceeds to demonstrate that, given these definitions, certain widely accepted ideas (absolute time; length independent of motion) were invalid.

Develop an Hypothesis

A hypothesis includes a suggested explanation of the subject. It will generally provide a causal explanation or propose some correlation.

Observations have the general form of existential statements, stating that some particular instance of the phenomena has some characteristic. Causal explanations have the general form of universal statements, stating that every instance of the phenomena has a particular characteristic. It is not deductively valid to infer a universal statement from any series of particular observations. This is the problem of induction. Many solutions to this problem have been suggested, including falsifiability and Bayesian inference. Bayesian inference has been claimed as a suitable logical basis for discriminating between conflicting hypotheses. This method uses an estimate of the degree of belief in a hypothesis before the advent of some evidence to give a numerical value to the degree of belief in the hypothesis after the advent of the evidence. Because it relies on subjective degrees of belief, it is not able to provide a completely objective account of induction.

Scientists use whatever they can—their own creativity, ideas from other fields, induction, or even systematic guessing, or any other methods available—to come up with possible explanations for the phenomenon under study. There are no definitive guidelines for the production of new hypotheses. The history of science is filled with stories of scientists claiming a "flash of inspiration", or a hunch, which then motivated them to look for evidence to support or refute their idea. Michael Polanyi made such creativity the centrepiece of his discussion of methodology.

Prediction from the hypothesis

A useful hypothesis will enable predictions to be made, by deductive reasoning, that can be experimentally assessed. If results contradictory to the predictions are found, the hypothesis under test is incorrect or incomplete, requiring either revision or abandonment. If results confirming the hypothesis are found, the hypothesis might be correct, but is always subject to further test.

Experiment

Once a prediction is made, an experiment is designed to test it. The experiment may seek either confirmation or falsification of the hypothesis.

Scientists assume an attitude of openness and accountability on the part of those conducting an experiment. Detailed recordkeeping is essential, to aid in recording and reporting on the experimental results, and providing evidence of the effectiveness and integrity of the procedure. They will also assist in reproducing the experimental results.

Integrity may be augmented by the introduction of a control. Two virtually identical experiments are run, in only one of which the factor being tested is varied. This serves to further isolate any causal phenomena. For example in testing a drug it is important to carefully test that the supposed effect of the drug is produced only by the drug itself. Doctors may do this with a double-blind study: two virtually identical groups of patients are compared, one of which receives the drug and one of which receives a placebo. Neither the patients nor the doctor know who is getting the real drug, isolating its effects.

Once the experiment is complete, the researcher determines whether the results (or data) gathered are what was predicted. If the experimental conclusions fail to match the predictions/hypothesis, then one returns to the failed hypothesis and re-iterates the process. If the experiment(s) appears "successful" - i.e. fits the hypothesis - then the results are to be published in a way which allows others (in theory) to reproduce the same experiments and results.

Evaluation and iteration

Testing and improvement

Verification

Peer review evaluation

Reproducibility

On the other hand, peer review of new discoveries is sometimes not very open-minded. The proposed existence of infectious protein particles by Stanley Prusiner in 1982 caused much scoffing and even hostility since it seemingly contradicted the central dogma of molecular biology, yet he won the 1997 Nobel Prize in physiology or medicine for the discovery of prions. Similarly, dark matter wasn't believed when first theorized in 1933 by Fritz Zwicky, nor when observationally confirmed by Vera Rubin in 1978, but after multiple independent confirmations, dark matter is now accepted in astrophysics.

Reevaluation

Evidence and assumptions

Elegance of hypothesis

Philosophical issues

The material presented below is intended to show that, as with all philosophical topics, some of the issues surrounding the scientific method are neither straightforward nor simple.

Theory-dependence of observation

The scientific method depends on observation, in defining the subject under investigation and in performing experiments.

Observation involves perception, and so is a cognitive process. That is, one does not make an observation passively, but is actively involved in distinguishing the thing being observed from surrounding sensory data. Observations, therefore, depend on some underlying understanding of the way in which the world functions, and that understanding may influence what is perceived, noticed, or deemed worthy of consideration. (See the Sapir-Whorf Hypothesis for an early version of this understanding of the impact of cultural artifacts on our perceptions of the world.)

It is reasonable, when someone claims to have made an observation, to ask them to justify their claim. Such a justification must itself make reference to the theory - the operational definitions and deductions from hypotheses - in which the observation is embedded. But this means, again, that observation by itself cannot be used to decide between competing theories. Empirical observation, during experimentation, is used to determine the acceptability of a hypothesis. Observation could only do this "neutrally" if the theory on which the observation depends and the theory being verified were independent of each other.

Kuhn denied that it is ever possible to isolate the theory being tested from influence by the theory in which the making of observations is grounded, arguing that observations always rely on a specific paradigm, and that it is not possible to evaluate competing paradigms independently. By "paradigm" he meant, essentially, a logically consistent "portrait" of the world, one that involves no logical contradictions. More than one such logically consistent construct can paint a usable likeness of the world, but it is pointless to pit them against each other, theory against theory. Neither is a standard by which the other can be judged. Instead, the question is which "portrait" is judged by some set of people to promise the most in terms of “puzzle solving”.

For Kuhn, the choice of paradigm was sustained by, but not ultimately determined by, logical processes. The individual's choice between paradigms involves setting two or more “portraits" against the world and deciding which likeness is most promising. In the case of a general acceptance of one paradigm or another, Kuhn believed that it represented the consensus of the community of scientists. Acceptance or rejection of some paradigm is, he argued, more a social than a logical process.

That observation is embedded in theory does not mean that observations are irrelevant to science. Scientific understanding derives from observation, but the acceptance of scientific statements is dependent on the related theoretical background or paradigm a well as on observation. Coherentism and scepticism offer alternatives to foundationalism for dealing with the difficulty of grounding scientific theories in something more than observations.

Indeterminacy of theory under empirical test

The Quine-Duhem thesis points out that any theory can be made compatible with any empirical observation by the addition of suitable ad hoc hypotheses. This is analogous to the way in which an infinite number of curves can be drawn through any set of data points on a graph.

This thesis was accepted by Karl Popper, leading him to reject naïve falsification in favour of 'survival of the fittest', or most falsifiable, of scientific theories. In Popper's view, any hypothesis that does not make testable predictions is simply not science. Such a hypothesis may be useful or valuable, but it cannot be said to be science. Confirmation holism, developed by W. V. Quine, states that empirical data is not sufficient to make a judgment between theories. A theory can always be made to fit with the empirical data available.

That empirical evidence does not serve to determine between alternat theories does not imply that all theories are of equal value. Rather than pretending to use a universally applicable methodological principle, the scientist is making a personal choice when she chooses some particular theory over another.

One result of this is that specialists in the philosophy of science stress the requirement that observations made for the purposes of science be restricted to intersubjective objects. That is, science is restricted to those areas where there is general agreement on the nature of the observations involved. It is comparatively easy for folk to agree on observations of physical phenomena, harder for them to agree on observations of socia or mental phenomena, and difficult in the extreme to reach agreement on matters of theology or ethics.

Demarcation

If observation cannot act as a theory-independent foundation for the Source | Copyright

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