Scientific method is a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. It
is based on gathering observable, empirical and measurable evidence subject to specific principles of reasoning, the collection of data through
observation and experimentation, and the formulation and testing of hypotheses.
Although procedures vary from one field of inquiry to another, identifiable features distinguish scientific inquiry from other methodologies of
knowledge. Scientific researchers propose hypotheses as explanations of phenomena, and design experimental studies to test these hypotheses. These
steps must be repeatable in order to predict dependably any future results. Theories that encompass wider domains of inquiry may bind many hypotheses
together in a coherent structure. This in turn may help form new hypotheses or place groups of hypotheses into context.
The following set of methodological elements and organization of procedures tends to be more characteristic of natural sciences and experimental
psychology than of social sciences. In the social sciences mathematical and statistical methods of verification and hypotheses testing may be less
stringent. Nonetheless the cycle of hypothesis, verification and formulation of new hypotheses will resemble the cycle described below.
The essential elements of a scientific method are iterations, recursions, interleavings, and orderings of the following:
* Characterizations (Quantifications, observations, and measurements)
* Hypotheses (theoretical, hypothetical explanations of observations and measurements)
* Predictions (reasoning including logical deduction from hypothesis and theory)
* Experiments (tests of all of the above)
Imre Lakatos and Thomas Kuhn had done extensive work on the "theory laden" character of observation. Kuhn (1961) said the scientist generally has a
theory in mind before designing and undertaking experiments so as to make empirical observations, and that the "route from theory to measurement can
almost never be traveled backward". This implies that the way in which theory is tested is dictated by the nature of the theory itself, which led
Kuhn (1961, p. 166) to argue that "once it has been adopted by a profession ... no theory is recognized to be testable by any quantitative tests that
it has not already passed".
Each element of a scientific method is subject to peer review for possible mistakes. These activities do not describe all that scientists do (see
below) but apply mostly to experimental sciences (e.g., physics, chemistry). The elements above are often taught in the educational system.
Scientific method is not a recipe: it requires intelligence, imagination, and creativity. It is also an ongoing cycle, constantly developing more
useful, accurate and comprehensive models and methods. For example, when Einstein developed the Special and General Theories of Relativity, he did not
in any way refute or discount Newton's Principia. On the contrary, if the astronomically large, the vanishingly small, and the extremely fast are
reduced out from Einstein's theories — all phenomena that Newton could not have observed — Newton's equations remain. Einstein's theories are
expansions and refinements of Newton's theories, and observations that increase our confidence in them also increase our confidence in Newton's
approximations to them.
A linearized, pragmatic scheme of the four points above is sometimes offered as a guideline for proceeding:
1. Define the question
2. Gather information and resources (observe)
3. Form hypothesis
4. Perform experiment and collect data
5. Analyze data
6. Interpret data and draw conclusions that serve as a starting point for new hypothesis
7. Publish results
8. Retest (frequently done by other scientists)
The iterative cycle inherent in this step-by-step methodology goes from point 3 to 6 back to 3 again.
While this schema outlines a typical hypothesis/testing method, it should also be noted that a number of philosophers, historians and sociologists of
science (perhaps most notably Paul Feyerabend) claim that such descriptions of scientific method have little relation to the ways science is actually
The "operational" model combines the concepts of factory-style processing, operational definition, and utility:
The essential elements of a scientific method are operations, observations, models, and a utility function for evaluating models.
* Operation - Some action done to the system being investigated
* Observation - What happens when the operation is done to the system
* Model - A fact, hypothesis, theory, or the phenomenon itself at a certain moment
* Utility Function - A measure of the usefulness of the model to explain, predict, and control, and of the cost of use of it. One of the elements of
any scientific utility function is the refutability of the model. Another is its simplicity, on the Principle of Parsimony also known as Occam's
The Keystones of Science project, sponsored by the journal Science, has selected a number of scientific articles from that journal and annotated them,
illustrating how different parts of each article embody scientific method. Here is an annotated example of this scientific method example titled
Microbial Genes in the Human Genome: Lateral Transfer or Gene Loss?.
is the change in the inherited traits of a population from generation to generation. These traits are the expression of genes that are copied and
passed on to offspring during reproduction. Mutations in these genes can produce new or altered traits, resulting in heritable differences (genetic
variation) between organisms. New traits can also come from transfer of genes between populations, as in migration, or between species, in horizontal
gene transfer. Evolution occurs when these heritable differences become more common or rare in a population, either non-randomly through natural
selection or randomly through genetic drift.
Natural selection is a process that causes heritable traits that are helpful for survival and reproduction to become more common, and harmful traits
to become more rare. This occurs because organisms with advantageous traits pass on more copies of these heritable traits to the next generation. Over
many generations, adaptations occur through a combination of successive, small, random changes in traits, and natural selection of those variants
best-suited for their environment. In contrast, genetic drift produces random changes in the frequency of traits in a population. Genetic drift arises
from the role chance plays in whether a given individual will survive and reproduce.
One definition of a species is a group of organisms that can reproduce with one another and produce fertile offspring. However, when a species is
separated into populations that are prevented from interbreeding, mutations, genetic drift, and the selection of novel traits cause the accumulation
of differences over generations and the emergence of new species. The similarities between organisms suggest that all known species are descended from
a common ancestor (or ancestral gene pool) through this process of gradual divergence.
as a theory and fact
"Fact" vs "Theory"
A "fact" in science is an observation.
A "theory" in science is an explanation of the observations.
Scientists use many specialized terms, frequently attributing to common words meanings foreign to the layperson. In particular,
* A fact is an observation or a piece of data. Facts can include objective measurements which can be either pieces of verifiable evidence, or the
results of an experiment which can be repeated over and over again by different people. For example, there are many observations of gravity and
measurements of gravity. Every time an apple is dropped and it falls, an observation of gravity has been made. Gravity is measured every time
something is weighed. So gravity can be described by scientists as a fact. This is because there is a collection of gravity observations that need to
be explained. Objective observations are facts in scientific language.
* Theories in science are different from facts. Scientific theories describe the coherent framework into which observable data fit. There have
been many theories that attempt to explain the fact of gravity. That is, scientists ask what is gravity, and what causes it. They develop a model to
explain gravity, a theory of gravity. Predictions can be made and tested based on this theory. Many explanations of gravity that qualify as a Theory
of Gravity have been proposed over the centuries: Aristotle's, Galileo's, Newton's, and now Einstein's. So gravity is also a theory. In science,
current theory is the theory that has no equally acceptable alternate theory, and has not been falsified, that is there have been no observations made
which contradict it to this point and, indeed, every observation ever made either supports current theory or at least does not falsify it (see Karl
Popper). In no case did gravity disappear when a new theory was created; instead, the explanation for gravity was refined and improved.
G = Gravity... E = Evolution
G... Things falling is an observation of the pull of bodies towards each other.
E... Fruit flies changing generation to generation is an observation of generational organism change.
G... Bodies pulling towards each other is called gravity.
E... Organisms changing generation to generation is called evolution.
Gravity is a "fact". Evolution is a "fact".
An explanation for the "facts" of gravity.
An explanation for the "facts" of evolution.
Aristotle and Galileo created explanations of the "fact" of gravity. These are now obsolete explanations. Lamarckism, Transmutationism and
Orthogenesis were created as explanations of the "fact" of evolution. These are now discredited explanations.
Newton's explanation of gravity is approximately correct but required refinement.
Darwin's explanation of evolution is approximately correct, but required refinement.
Einstein's explanation is a refinement of Newton's explanation of gravity. Einstein's explanation is currently the most accepted explanation of the
"fact" of gravity.
The Neo-Darwinist explanation is a refinement of Darwin's explanation of evolution. Neo-Darwinism is currently the most accepted explanation of the
"fact" of evolution.
Einstein's explanation of the "fact" of gravity is called The General theory of relativity.
The Neo-Darwinist explanation of the "fact" of evolution is the latest and most widely accepted Theory of Evolution.
Gravity is a "fact" and a "theory." Evolution is a "fact" and a "theory."
This confusion between "fact" and "theory" in the study of evolution was explored in a well-known quote by paleontologist Stephen Jay Gould:
" Evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts
are the world's data. Theories are structures of ideas that explain and interpret facts. Facts do not go away when scientists debate rival theories
to explain them. Einstein's theory of gravitation replaced Newton's, but apples did not suspend themselves in mid-air, pending the outcome. And
humans evolved from ape-like ancestors whether they did so by Darwin's proposed mechanism or by some other yet to be discovered."