Different views on what is known, how it is known, and what can be known are connected. Plato distinguished the realms of things into the visible and the intelligible The Republic , a, in Cooper Only the latter, the Forms, could be objects of knowledge. The intelligible truths could be known with the certainty of geometry and deductive reasoning. What could be observed of the material world, however, was by definition imperfect and deceptive, not ideal.
The Platonic way of knowledge therefore emphasized reasoning as a method, downplaying the importance of observation. Aristotle disagreed, locating the Forms in the natural world as the fundamental principles to be discovered through the inquiry into nature Metaphysics Z , in Barnes Aristotle is recognized as giving the earliest systematic treatise on the nature of scientific inquiry in the western tradition, one which embraced observation and reasoning about the natural world. In the Prior and Posterior Analytics , Aristotle reflects first on the aims and then the methods of inquiry into nature.
A number of features can be found which are still considered by most to be essential to science. For Aristotle, empiricism, careful observation but passive observation, not controlled experiment , is the starting point. The aim is not merely recording of facts, though. The aims of discovery, ordering, and display of facts partly determine the methods required of successful scientific inquiry. Also determinant is the nature of the knowledge being sought, and the explanatory causes proper to that kind of knowledge see the discussion of the four causes in the entry on Aristotle on causality.
In addition to careful observation, then, scientific method requires a logic as a system of reasoning for properly arranging, but also inferring beyond, what is known by observation. Methods of reasoning may include induction, prediction, or analogy, among others.
The basic aim and method of inquiry identified here can be seen as a theme running throughout the next two millennia of reflection on the correct way to seek after knowledge: carefully observe nature and then seek rules or principles which explain or predict its operation.
The Aristotelian corpus provided the framework for a commentary tradition on scientific method independent of science itself cosmos versus physics. In analysis, a phenomena was examined to discover its basic explanatory principles; in synthesis, explanations of a phenomena were constructed from first principles. During the Scientific Revolution these various strands of argument, experiment, and reason were forged into a dominant epistemic authority. The 16 th —18 th centuries were a period of not only dramatic advance in knowledge about the operation of the natural world—advances in mechanical, medical, biological, political, economic explanations—but also of self-awareness of the revolutionary changes taking place, and intense reflection on the source and legitimation of the method by which the advances were made.
The struggle to establish the new authority included methodological moves. The Book of Nature, according to the metaphor of Galileo Galilei — or Francis Bacon — , was written in the language of mathematics, of geometry and number.
This motivated an emphasis on mathematical description and mechanical explanation as important aspects of scientific method. Through figures such as Henry More and Ralph Cudworth, a neo-Platonic emphasis on the importance of metaphysical reflection on nature behind appearances, particularly regarding the spiritual as a complement to the purely mechanical, remained an important methodological thread of the Scientific Revolution see the entries on Cambridge platonists ; Boyle ; Henry More ; Galileo.
In Novum Organum , Bacon was critical of the Aristotelian method for leaping from particulars to universals too quickly. The syllogistic form of reasoning readily mixed those two types of propositions. Bacon aimed at the invention of new arts, principles, and directions.
The community of scientists could then climb, by a careful, gradual and unbroken ascent, to reliable general claims. Whewell would later criticize Bacon in his System of Logic for paying too little attention to the practices of scientists. It is to Isaac Newton — , however, that historians of science and methodologists have paid greatest attention. Given the enormous success of his Principia Mathematica and Opticks , this is understandable. This was viewed mainly on the continent as insufficient for proper natural philosophy.
The Regulae counter this objection, re-defining the aims of natural philosophy by re-defining the method natural philosophers should follow. The scientist was not to invent systems but infer explanations from observations, as Bacon had advocated. This would come to be known as inductivism. In the century after Newton, significant clarifications of the Newtonian method were made. Colin Maclaurin — , for instance, reconstructed the essential structure of the method as having complementary analysis and synthesis phases, one proceeding away from the phenomena in generalization, the other from the general propositions to derive explanations of new phenomena.
The emphasis was often the same, as much on the character of the scientist as on their process, a character which is still commonly assumed. The scientist is humble in the face of nature, not beholden to dogma, obeys only his eyes, and follows the truth wherever it leads.
It was certainly Voltaire — and du Chatelet — who were most influential in propagating the latter vision of the scientist and their craft, with Newton as hero. Scientific method became a revolutionary force of the Enlightenment. See also the entries on Newton , Leibniz , Descartes , Boyle , Hume , enlightenment , as well as Shank for a historical overview. Not all 18 th century reflections on scientific method were so celebratory.
Both Hume and Kant influenced the methodological reflections of the next century, such as the debate between Mill and Whewell over the certainty of inductive inferences in science. The debate between John Stuart Mill — and William Whewell — has become the canonical methodological debate of the 19 th century.
Although often characterized as a debate between inductivism and hypothetico-deductivism, the role of the two methods on each side is actually more complex. On the hypothetico-deductive account, scientists work to come up with hypotheses from which true observational consequences can be deduced—hence, hypothetico-deductive.
Because Whewell emphasizes both hypotheses and deduction in his account of method, he can be seen as a convenient foil to the inductivism of Mill. Knowledge is a product of the objective what we see in the world around us and subjective the contributions of our mind to how we perceive and understand what we experience, which he called the Fundamental Ideas. Both elements are essential according to Whewell, and he was therefore critical of Kant for too much focus on the subjective, and John Locke — and Mill for too much focus on the senses.
An idea can be fundamental even if it is necessary for knowledge only within a given scientific discipline e. This distinguishes fundamental ideas from the forms and categories of intuition of Kant. See the entry on Whewell. Clarifying fundamental ideas would therefore be an essential part of scientific method and scientific progress. The subjective plays a role through what Whewell calls the Colligation of Facts, a creative act of the scientist, the invention of a theory.
A theory is then confirmed by testing, where more facts are brought under the theory, called the Consilience of Inductions. Whewell felt that this was the method by which the true laws of nature could be discovered: clarification of fundamental concepts, clever invention of explanations, and careful testing.
Down-playing the discovery phase would come to characterize methodology of the early 20 th century see section 3.
Mill, in his System of Logic , put forward a narrower view of induction as the essence of scientific method. For Mill, induction is the search first for regularities among events.
Among those regularities, some will continue to hold for further observations, eventually gaining the status of laws. One can also look for regularities among the laws discovered in a domain, i. These five methods look for circumstances which are common among the phenomena of interest, those which are absent when the phenomena are, or those for which both vary together.
The methods advocated by Whewell and Mill, in the end, look similar. Both involve inductive generalization to covering laws. They differ dramatically, however, with respect to the necessity of the knowledge arrived at; that is, at the meta-methodological level see the entries on Whewell and Mill entries. The quantum and relativistic revolutions in physics in the early 20 th century had a profound effect on methodology.
Conceptual foundations of both theories were taken to show the defeasibility of even the most seemingly secure intuitions about space, time and bodies. Certainty of knowledge about the natural world was therefore recognized as unattainable. Instead a renewed empiricism was sought which rendered science fallible but still rationally justifiable.
Analyses of the reasoning of scientists emerged, according to which the aspects of scientific method which were of primary importance were the means of testing and confirming of theories. A distinction in methodology was made between the contexts of discovery and justification. The distinction could be used as a wedge between the particularities of where and how theories or hypotheses are arrived at, on the one hand, and the underlying reasoning scientists use whether or not they are aware of it when assessing theories and judging their adequacy on the basis of the available evidence.
By and large, for most of the 20 th century, philosophy of science focused on the second context, although philosophers differed on whether to focus on confirmation or refutation as well as on the many details of how confirmation or refutation could or could not be brought about. By the mid th century these attempts at defining the method of justification and the context distinction itself came under pressure.
During the same period, philosophy of science developed rapidly, and from section 4 this entry will therefore shift from a primarily historical treatment of the scientific method towards a primarily thematic one.
Carnap attempted to show that a scientific theory could be reconstructed as a formal axiomatic system—that is, a logic. That system could refer to the world because some of its basic sentences could be interpreted as observations or operations which one could perform to test them. The rest of the theoretical system, including sentences using theoretical or unobservable terms like electron or force would then either be meaningful because they could be reduced to observations, or they had purely logical meanings called analytic, like mathematical identities.
This has been referred to as the verifiability criterion of meaning. According to the criterion, any statement not either analytic or verifiable was strictly meaningless. Although the view was endorsed by Carnap in , he would later come to see it as too restrictive Carnap Another familiar version of this idea is operationalism of Percy William Bridgman. In The Logic of Modern Physics Bridgman asserted that every physical concept could be defined in terms of the operations one would perform to verify the application of that concept.
Making good on the operationalisation of a concept even as simple as length, however, can easily become enormously complex for measuring very small lengths, for instance or impractical measuring large distances like light years.
He pointed out that universal generalizations, such as most scientific laws, were not strictly meaningful on the criterion. Verifiability and operationalism both seemed too restrictive to capture standard scientific aims and practice. The tenuous connection between these reconstructions and actual scientific practice was criticized in another way.
In both approaches, scientific methods are instead recast in methodological roles. Measurements, for example, were looked to as ways of giving meanings to terms. The aim of the philosopher of science was not to understand the methods per se , but to use them to reconstruct theories, their meanings, and their relation to the world.
When scientists perform these operations, however, they will not report that they are doing them to give meaning to terms in a formal axiomatic system.
This disconnect between methodology and the details of actual scientific practice would seem to violate the empiricism the Logical Positivists and Bridgman were committed to. The view that methodology should correspond to practice to some extent has been called historicism, or intuitionism. We turn to these criticisms and responses in section 3. Positivism also had to contend with the recognition that a purely inductivist approach, along the lines of Bacon-Newton-Mill, was untenable.
There was no pure observation, for starters. All observation was theory laden. Theory is required to make any observation, therefore not all theory can be derived from observation alone. See the entry on theory and observation in science.
Even granting an observational basis, Hume had already pointed out that one could not deductively justify inductive conclusions without begging the question by presuming the success of the inductive method. Likewise, positivist attempts at analyzing how a generalization can be confirmed by observations of its instances were subject to a number of criticisms.
Goodman and Hempel both point to paradoxes inherent in standard accounts of confirmation. Recent attempts at explaining how observations can serve to confirm a scientific theory are discussed in section 4 below.
The standard starting point for a non-inductive analysis of the logic of confirmation is known as the Hypothetico-Deductive H-D method. In its simplest form, a sentence of a theory which expresses some hypothesis is confirmed by its true consequences.
As noted in section 2 , this method had been advanced by Whewell in the 19 th century, as well as Nicod and others in the 20 th century. Some hypotheses conflicted with observable facts and could be rejected as false immediately. Others needed to be tested experimentally by deducing which observable events should follow if the hypothesis were true what Hempel called the test implications of the hypothesis , then conducting an experiment and observing whether or not the test implications occurred.
If the experiment showed the test implication to be false, the hypothesis could be rejected. If the experiment showed the test implications to be true, however, this did not prove the hypothesis true.
The degree of this support then depends on the quantity, variety and precision of the supporting evidence. Falsification is deductive and similar to H-D in that it involves scientists deducing observational consequences from the hypothesis under test. For Popper, however, the important point was not the degree of confirmation that successful prediction offered to a hypothesis.
The crucial thing was the logical asymmetry between confirmation, based on inductive inference, and falsification, which can be based on a deductive inference. This simple opposition was later questioned, by Lakatos, among others. See the entry on historicist theories of scientific rationality. Popper stressed that, regardless of the amount of confirming evidence, we can never be certain that a hypothesis is true without committing the fallacy of affirming the consequent.
Instead, Popper introduced the notion of corroboration as a measure for how well a theory or hypothesis has survived previous testing—but without implying that this is also a measure for the probability that it is true. Popper was also motivated by his doubts about the scientific status of theories like the Marxist theory of history or psycho-analysis, and so wanted to demarcate between science and pseudo-science. Popper saw this as an importantly different distinction than demarcating science from metaphysics.
The rationale behind this conclusion is that because all observations of cell behavior show that cells are only derived from other cells, this assertion must be always true. Inductive reasoning, however, is not immune to mistakes and limitations. And this is where limited observations can lead to erroneous conclusions reasoned inductively. In another example, if one never has seen a swan that is not white, they might conclude that all swans are white, even when we know that black swans do exist, however rare they may be.
The universally accepted scientific method, as it is used in science laboratories today, is grounded in hypothetico-deductive reasoning. Research progresses via iterative empirical testing of formulated, testable hypotheses formulated through inductive reasoning. A testable hypothesis is one that can be rejected falsified by empirical observations, a concept known as the principle of falsification.
Initially, ideas and conjectures are formulated. Experiments are then performed to test them. If the body of evidence fails to reject the hypothesis, the hypothesis stands. It stands however until and unless another even singular empirical observation falsifies it. However, just as with inductive reasoning, hypothetico-deductive reasoning is not immune to pitfalls—assumptions built into hypotheses can be shown to be false, thereby nullifying previously unrejected hypotheses.
The bottom line is that science does not work to prove anything about the natural world. Instead, it builds hypotheses that explain the natural world and then attempts to find the hole in the reasoning i.
Therefore, it is important to understand that science uses controlled experiments in order to test hypotheses and contribute new knowledge. So what exactly is a controlled experiment, then? Let us take a practical example. Our starting hypothesis is the following: we have a novel drug that we think inhibits the division of cells, meaning that it prevents one cell from dividing into two cells recall the description of cell theory above.
This question will include one of the key starters, which are how, what when, why, where, who or which. The question you ask should also be measurable and answerable through experimentation. It is often something that can be measured with a numerical result, although behavioral results are part of the scientific method as well. Example: Perhaps, you want to test an experiment about the causal relationship between music and certain domesticated animals.
With your question formulated, conduct preliminary background research to prepare yourself for the experiment. You can find information through online searches or in your local library, depending on the question you are asking and the nature of the background data.
You may also find previous studies and experiments that can help with your process and conclusions. In this case, you might start by reviewing previous scientific studies for animal experiments related to their reactions to music. Key to finding pertinent information might be looking at studies that study animal behavior in relation to art or domestic animals directly affected by music.
A hypothesis is an educated guess that seeks to answer a question that can be systematically tested. Your hypothesis should also include your predictions that you can measure through experimentation and research. If I play rock-and-roll music, my dog and cat will leave the room. Next, test your hypothesis by conducting an experiment. Your experiment is a way to quantifiably test your predictions and should be able to be repeated by another scientist. Example: You decide to test it out: You bring the cat and dog into the same room where a sound system is available.
You play classical music at a low volume. Both animals remain in the room. In an experiment a researcher manipulates certain variables and measures their effect on other variables in a controlled environment. Descriptive studies describe the nature of the relationship between the intended variables, without looking at cause or effect.
A case study covers one specific example in which something unusual has occurred. This is often done in extreme or rare cases, usually with a single subject. Surveys are used with large groups of people who answer questions about specific subjects. Non-descriptive studies use correlational methods to predict the relationship between two or more intended variables. Verifiability means that an experiment must be replicable by another researcher. To achieve verifiability, researchers must make sure to document their methods and clearly explain how their experiment is structured and why it produces certain results.
Predictability in a scientific theory implies that the theory should enable us to make predictions about future events. The precision of these predictions is a measure of the strength of the theory.
Falsifiability refers to whether a hypothesis can disproved. For a hypothesis to be falsifiable, it must be logically possible to make an observation or do a physical experiment that would show that there is no support for the hypothesis.
Even when a hypothesis cannot be shown to be false, that does not necessarily mean it is not valid. Future testing may disprove the hypothesis.
This does not mean that a hypothesis has to be shown to be false, just that it can be tested. To determine whether a hypothesis is supported or not supported, psychological researchers must conduct hypothesis testing using statistics.
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