''The ''scientific method'' is a sequence or collection of procedures that are considered characteristic of scientific investigation and the acquisition of new scientific Knowledge. This method is believed to distinguish science from other intellectual traditions, such as painting, philosophy or theology.
In his enunciation of a 'scientific 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 described a rational procedure for establishing causation between phenomena. Argument by analogy, which was popular in the ecclesiastical scholarly tradition, became much less acceptable in science (or ''natural philosophy,'' as it was still called).
It is common to speak as though a single approach such as Roger Bacon's is how scientists operate all the time. Many scientists, historians, philosophers and sociologists regard this perspective as naïve, and see the actual operation of science as more complicated and haphazard. A common element of scientific research involves the vetting of theories in a way that seems more formal and rigorous than the practices of other disciplines and traditions.
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.'' Whether formularizable or not, scientific method represents a standard of proficiency and reliability.
__Scientific Method and the practice of science__
The study of Scientific Method is distinct from the practice of science and is more a part of the philosophy, history and sociology of science than of science itself. Such studies have limited direct impact on day-to-day scientific practice.
In actual science (meaning, in this context, the activities of those described as scientists) the primary constraints are:
* Publication, i.e. Peer Review
* Resources (mostly, funding)
It has not always been like this: in the old days of the ''gentleman scientist'' funding (and to a lesser extent publication) were far weaker constraints.
Both of these constraints indirectly bring in the idealised method - work that too obviously violates the constraints will be difficult to publish and difficult to get funded. Journals do not require submitted papers to conform to anything more specific that ''good scientific practice'' and this is mostly enforced by peer review. Originality, importance and interest are more important - see for example the author guidelines for ''Nature'' http://www.nature.com/nature/submit/get_published/index.html.
__The idealized scientific method__
The essential elements of the scientific method are traditionally described as follows:
* ''Observe:'' Observe or read about a phenomenon.
* ''Hypothesize:'' Wonder about your observations, and invent a Hypothesis, (sometimes one's hypothesis is initially nothing more than a ''guess''), which could explain the phenomenon or set of facts that you have observed.
* ''Test'' a hypothesis
** ''Predict:'' Use the logical consequences of your hypothesis to predict results (e.g., measurable experimental values) that must be found if the hypothesis is to be judged correct -- whether it is 'complete' or not.
** ''Experiment:'' Perform experiments to test those predictions. (Note that great precision regarding a negative result might not be required to falsify a hypothesis.)
*''Conclude:'' Failure to see the predicted results from a well designed and implemented experiment is clear indication that the hypothesis is defective. Try again. Seeing the predicted results is an indication that the hypothesis is acceptable though not 'confirmation' or 'proof' of its correctness.
** ''Evaluate:'' Search for other possible explanations of the result until you can propose no better account of your data.
* ''Formulate a new hypothesis'' which may better explain the experimental data and the original observation.
* ''Repeat:'' The steps above, and the experimental methods, should be described in sufficient detail to allow a competent scientist to repeat/verify the results.
These activities do not describe all that scientists do. The simplified method described above is often used in teaching.
This idealised process is often misinterpreted as applying to scientists individually rather than to the scientific enterprise as a whole. Science is a social activity, and one scientist's theory or proposal cannot become accepted unless it has become known to others (usually via publication, ideally Peer Reviewed publication), criticised, and finally accepted by the scientific community.
The scientific method begins with observation. Observation often demands careful ''measurement''.
Logically preceeding observation, but in practice strongly interlinked, is the need for accurate definitions of the items to be observed.
''Operational Definitions'' of measurements and other relevant concepts are not scientific hypotheses; they are not ''falsifiable''; they are simply a way to ensure that everyone is talking about, experimentally testing, etc the same thing.
By definition, words 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. Most prominently, Einsteins first paper on relativity begins by defining simultaneity and the means for determining length (which were skipped over by 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.
To explain the observation, scientists use whatever they can (their own creativity (currently not well understood), ideas from other fields, or even systematic guessing, or any other methods available) to come up with possible explanations for the phenomenon under study.
In the twentieth century Karl Popper introduced the idea that a hypothesis must be falsifiable; that is, it must be capable of being demonstrated wrong. This was similar to C S Peirce's position, Falibilism, which Popper credited after he became aware of Peirce's work.
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. The story about an apple falling on Isaac Newton's head and inspiring his theory of gravity is a popular example of this; there In contrast, Kekule's account of the inspiration (in the mid 19th century) for his hypothesis of the structure of the benzene-ring (day dreaming of snakes biting their own tails while he was dozing in an omnibus) is better attested, in his own words from the time. Though primarily an engineer and not a scientist, Thomas Edison was famously quoted in the 20th century as saying that ''genius is 1% inspiration and 99% perspiration'', but he sought to capture the creative insights that may occur during the twilight between wakefulness and sleep. He made a frequent practice of holding something in his hand as he drifted off to sleep in his chair so that as soon as he entered sleep he would be awakened by the sound of the dropping weight. He would then be able to remember what he had envisioned during his most recent twilight state. Hypotheses come from many sources and there is no method known which always, or even mostly, generates ''good'' ones.
An hypothesis must make specific predictions; these predictions must be testable, typically with concrete measurements. If results contradictory to the predictions are found, the hypothesis under test is wrong (requiring either revision or abandonment). If results consistent with the hypothesis are found, the hypothesis might be correct, but is always subject to further tests. In Popper's view, any hypothesis that does not make testable predictions is simply not science. Something else useful and valuable perhaps (or perhaps not), but not science.
For instance, Albert Einstein's General Relativity makes several specific predictions about the observable structure of space-time, such as a prediction that light bends in a gravitational field, and that the amount of bending depends in a precise way on the strength of the gravitational field. Observations made during a 1919 solar eclipse supported the hypothesis (i.e., General Relativity) as against those of other hypotheses which predicted different results, and falsified any theory which predicted something else, e.g., Newtonian gravitation.
Deductive Reasoning is the way in which predictions are developed with which to test a hypothesis.
Probably the most important aspect of scientific reasoning is the demand for empirical verification: One's experimental observations must be verifiable by other researchers. Verification is the process of determining whether the hypothesis is in accord with empirical evidence, both newly acquired and already existing. It is the necessary complement to predictions.
Ideally, the experiments performed should be fully described so that anyone can reproduce them, and many scientists should independently verify every hypothesis. Results that can be obtained from experiments performed by many are termed ''reproducible'' and are given much greater weight in evaluating hypotheses than is given to non-reproducible results.
Scientists must design their experiments carefully. For example, if the measurements are difficult to make, or subject to observer bias, one must be careful to avoid distorting the results because of influences that arise from the experimenter's wishes. When experimenting on complex systems, one must be careful to isolate the effect being tested from other possible causes of the intended effect (this results in a ''controlled'' experiment).
In testing a drug, for example, it is important to carefully test that the supposed effect of the drug is produced only by the drug itself, and not by the placebo effect or by random chance. Doctors do this with what is called a double-blind study: two groups of patients are compared, one of which receives the drug and one of which receives a placebo. No patient in either group knows whether or not they are getting the real drug. Even the doctors or other personnel who interact with the patients do not know which patients are getting the drug under test and which are getting a fake drug (often sugar pills), so their knowledge cannot influence the patients either.
Falsificationism requires that any hypothesis, no matter how respected or time-honoured, be discarded once it is contradicted by reliable evidence, evidence that usually would come from new experiments. This is something of an oversimplification, since individual scientists will often hold on to their pet theory long after contrary evidence has been found. Max Planck is said to have suggested that new scientific theories are adopted when today's scientists finally die. This is not always a bad thing -- delayed adoption, not scientist mortality. Any theory can be made to correspond to the facts, simply by making a few adjustments—called ''auxiliary hypotheses''; so as to bring it into correspondence with the accepted observations. Additions to the turtle theory (invisibility, non-corporality, ...) are examples of this kind of thing. When to reject one theory and accept another ('better' one) is dependent on the judgement of individual scientists, rather than on some law or authority. As for the turtles, the members of the Flat Earth Society apparently still regard it as a tenable hypothesis, despite any observations made in the last few thousand years that might contradict it.
''All'' scientific knowledge is thus always in a state of flux, for at any time new evidence could be presented/discovered/developed that contradicts a long-held hypothesis. A particularly luminous example is the theory of light. Light had long been supposed to be made of particles. Isaac Newton, and before him many of the Classical Greeks, was convinced it was so, but his light-is-particles account was overturned by evidence in favor of a wave theory of light suggested most notably in the early 1800s by Thomas Young an English physician. Light as waves neatly explained the observed diffraction and interference of light when, to the contrary, the light-as-a-particle theory did not. The wave interpretation of light was widely held to be unassailably correct for most of the 19th century. Around the turn of the century, however, observations were made that a wave theory of light could not explain. This new set of observations could be accounted for by Max Planck's quantum theory (including the photoelectric effect and Brownian motion -- both from Albert Einstein), but not by a wave theory of light. Nor, for that matter, by the particle theory.
The failure of one hypothesis often does not lead smoothly to a new and successful hypothesis. In the case of light, the result of the ferment created by the two contrary sets of very well verified observations was the slow birth of Quantum Mechanics.
Experiments, whether widely accepted or not, should be performed by many different scientists so as to guard against bias, error, misunderstanding, fraud, etc. Those that seem to call into question, or even force rejection of, an existing previously satisfactory theory should be especially carefully checked. Scientific journals use a process of ''Peer Review'', in which scientists' papers describing experimental results and their conclusions are submitted to a panel of fellow scientists (who may or may not know the identity of the writer) for evaluation.
Scientists are rightly suspicious of results that do not go through this process. For example, the cold fusion experiments of Fleischmann and Pons were never peer reviewed—they were announced directly to the press before any other scientists were able to evaluate their efforts or reproduce their results. Their results have not been reproduced elsewhere else in the decades since; the press announcement was regarded at the time, by most nuclear physicists, as very likely wrong. Peer review may well have turned up problems and led to a closer examination of the experimental evidence Fleischmann, Pons, et al believed they had found. Paul Kammerer's experiments on acquired physical traits in amphibians (described in Arthur Koestler's The Midwife Toad) seem to have been deliberately faked, while the confusion in the 60s and 70s about 'polywater' seems to have been the result of micro contamination (and maybe some Cold War political oneupsmanship). Much embarrassment, and wasted effort, might have been avoided by proper peer review in many such cases.
On the other hand, peer review of new discoveries is sometimes not very open-minded. The discovery of prions caused much scoffing and even hostility to be directed against Stanley Prusiner, yet in 2004 his name is back in the news as having discovered an enzyme that may eliminate the threat caused by ''mad cow disease.''
Scientists tend to look for theories that are ''elegant'' or ''beautiful''. In contrast to the usual English use of these terms, scientists have more specific meanings in mind. ''Elegance'' (or ''beauty'') refers to the ability of a theory to neatly explain all known facts as simply as possible, or at least in a manner consistent with Occam's Razor while at the same time being aesthetically pleasing. This seems to be primarily a psychological bias, however often it has been useful in predicting correctly among competing theories. After all, 'more complex' (and so less psychologically satisfying) theories have often been required 'to account for the phenomena'. Superstring theory (even with all those dimensions) may turn out to be a theory which is both beautiful and yet as lean as it possibly could be. Turtlian world support theory has not been widely praised for either its predictive successes or its aesthetic qualities.
What has been called ''idealised scientific method '' in this article is one of many theories describing the way in which science works or should be conducted. These include Hypothetico-Deductive Method, falsification, the research programs of Imre Lakatos, and the scientific revolutions of Thomas Samuel Kuhn. It seems reasonable to ask how accurate it is in portraying the actual procedures followed by working scientists.
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.
The idealised scientific method claims to rely on observation as a main component of the process of verification.
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.)
So observations are embedded in theory. The idealised scientific method uses empirical observation to determine the acceptability of hypotheses during the verification phase. Observation could only do this neutrally if the theory on which the observation depends and the theory being verified were independent of each other.
Thomas 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 useful 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 provide the better likeness of the real world. In cases like the ''wave theory of light'' and the ''particle theory of light,'' both are internally consistent and both are not very satisfactory likenesses of light. Therefore, for practical purposes one may be chosen in certain circumstances, but the second may be chosen for all other circumstances.
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 is the more faithful likeness. 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 claimed, more a social than a logical process.
The W. V. Quine-Pierre Duhem thesis claims that any theory can be made compatible with any empirical observation by the addition of suitable ad hoc hypotheses. This thesis was accepted by Karl Popper, leading him to reject naÃ¯ve falsification in favour of 'survival of the fittest', or most falsifiable, of scientific theories.
Confirmation Holism, a theory developed by W. V. Quine and well accepted among professional philosophers of science, 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. Thus, shaping principles play a predominate role in what theories are accepted into the scientific community.
The idealised method adopts a foundationalist Epistemology, implicitly claiming that observations do not require justification and that observation is needed to get the scientific process underway. That observation is embedded in theory undermines its ability to act as the unjustified base of a foundationalist epistemology. That is, since it is reasonable, when someone claims to have made an observation, to ask them to justify their claim, the claim itself cannot function in the way required by foundationalism. That observation is embedded in theory does not mean that observations are irrelevant to science. Scientific understanding derives from observation, but the truth of scientific statements is as dependent on the related theoretical background or paradigm as it is on observation. Coherentism and Scepticism offer alternative ways of dealing with the difficulty of grounding scientific theories in something more than observations.
One result of this ambiguity is that most specialists in the philosophy of science stress the requirement that observations made for the purposes of science be restricted to ''intersubjective'' objects. Some negotiation about the meaning of words may be necessary, but people investigating some phenomenon should all be able to experience the same things given equal observational opportunities.
Scientific Method is often touted as determining which disciplines are scientific and which are not. Those which follow the scientific method might be considered sciences; those that do not are not. That is, method might be used as the criterion for demarcation between science and non-science.
If observation cannot act as a theory-independent foundation for the scientific enterprise, science becomes a cycle of hypothesising and verification embedded in a theoretical framework and tied to the 'real world' by the agreement of the scientific community. Popper's claim that only falsifiable statements are scientific does not help here. The Quine-Duhem thesis argues that it is not possible to ''prove'' that a statement is falsified; rather, falsification occurs when the scientific community agrees that a statement is falsified.
Assuming this to be true, it is not obvious how scientific debate differs in any logical way from the debates of, for example, historians. Both work within a cycle of hypothesising and verification, historians by reference to historical documents, scientists by reference to the experiments they construct. It is not possible to conduct experiments to test historical hypotheses, and that is not what this argument claims. History has already happened and cannot be rerun. Historians test their hypotheses by comparing them to historical sources and to other theories, whilst scientific theories are tested by comparing them to experimental results. What appears to differ is not the method, but the content, with historians taking historical documents as their verification criterion, while scientists use documentation from experiments.
One might argue that science occupies a special place because its experiments can be repeated, but using repetition as a demarcation criterion would disenfranchise areas that are at present considered to be science, such as palaeontology and cosmology.
Alternately, Kuhn claims that the explanatory success of science is explained by the way in which scientists are restricted to working within a particular paradigm.
Paul Feyerabend takes these arguments to their limit, arguing that science does not occupy a special place in terms of either its logic or method, and so that any claim to special authority made by scientists cannot be upheld. This leads to a particularly democratic and anarchist approach to knowledge formation.
__Science as a communal activity__
The ''idealised scientific method'' makes reference to the scientific community in the verification and evaluation of a scientific theory. Some consideration will lead to the conclusion that the role of the scientific community extends further than this.
In his book ''The Structure of Scientific Revolutions'' Kuhn argues that the process of observation and evaluation take place within a paradigm. 'A paradigm is what the members of a community of scientists share, and, conversely, a scientific community consists of men who share a paradigm' (postscript, part 1). On this account, science can be done only as a part of a community, and is inherently a communal activity.
For Kuhn the fundamental difference between science and other disciplines is in the way in which the communities function. Others, especially Feyerabend and some post-modernist thinkers, have argued that there is insufficient difference between social practices in science and other disciplines to maintain this distinction. It is apparent that social factors play an important and direct role in scientific method, but that they do not serve to differentiate science from other disciplines.
This is not an area of study in which it is possible to give a definitive account, because it is undergoing considerable change. It appears that positivist, empiricists and falsificationist theories are unable to satisfy their aim of giving as definitive account of the logic of science; it may also be that the sociology of science is incapable of accounting for the success of the scientific enterprise. In any case, it should be clear that the idealised scientific method is a source of ongoing debate and contention.
__Annotated list of related issues__
* Roger Bacon
* Francis Bacon
* Baconian Method
* Empirical Validation
* Paradigm, perhaps the most abused word in English.
* Thomas Kuhn wrote influentially on the sociology of scientific revolutions in The Structure of Scientific Revolutions.
* Paradigm Shift is a Kuhnian term referring to the change between one pervasively accepted theory (eg, Aristotian motion) and another (eg, Newtonian gravitation). Kuhn himself came to prefer other terminology.
The problem of induction questions the logical ground for
induction as a basis for science.
* Inductive Reasoning has appeared to some (most famously, to Sir Francis Bacon) to be at the core of scientific method; it also appears to be logically invalid.
* David Hume was the person who most famously and influentially pointed out the inadequacy of induction in generating true statements, scientific or not.
* Karl Popper offered one resolution, Falsifiability
* In his book ''Consilience: The Unity of Knowledge'' biologist E. O. Wilson suggests that we can validate the pragmatic value of induction by exploring the consilience of inductions obtained from different fields of science.
* Michael Polanyi
* Henri PoincarÃ©
* Tacit Knowledge
When Method goes wrong
* Bad Science
* Pathological Science