Object a has attributes a, b, c and another attribute d,
Object b has attributes a, b, c,
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Therefore, the b object has the property d.
The above "a" and "b" refer to different objects: or different individual objects, such as the earth and the sun; Or two different objects, such as plants and animals; Or it refers to different fields, such as the macro world and the micro world. The application of analogical reasoning is varied. Sometimes, a single object can be compared with another object. For example, in order to find out the effect and reaction of a new drug on human beings, it is often done with an individual animal, and then the answer is obtained by analogy.
The conclusion of analogy is possible. The conclusion of analogy is probable mainly for the following two reasons; On the one hand, there are not only similarities but also differences between objects. That is to say, although objects A and B are similar in a series of attributes (A, B, C), some attributes are always different because they are different objects. If the D attribute happens to be the particularity that A object is different from B object, then it is wrong for us to conclude that B image also has the D attribute. For example, although the Earth and Mars are similar in a series of attributes (planets in the solar system, existence of atmosphere, temperature suitable for life, etc.). ), there are creatures on the earth. Can we say that there are creatures on Mars? No, because Mars is different from Earth. Space science investigation shows that nothing has been found on Mars. On the other hand, there are many attributes in an object, some of which are inherent and some are accidental. For example, blood circulation is an inherent property of the human body, and eating eggs produces allergic reactions, which is sporadic for individuals. If the D attribute of analogy is an accidental attribute of one object, then another object probably has no D attribute.
As a reasoning method, analogy infers that another attribute is similar by comparing some attributes between different objects or different fields. It is not only different from deductive reasoning from the general to the individual, but also different from inductive reasoning from the individual to the general, but from one specific object or field to another.
Although analogy reasoning can be carried out between a certain kind of individual object and another kind of object, analogy reasoning cannot be carried out between a certain kind of individual object and its individual object. It is wrong to think that analogical reasoning is the compression of inductive reasoning and deductive reasoning. Analogical reasoning can only transition between two different objects or different fields.
Some people think that there is such analogical reasoning:
Individuals of class s have attributes a, b, c and d.
Class s has attributes a, b and c.
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Therefore, class s has attribute d.
This view is wrong, because it is based on subjective imagination and analogical reasoning mode to describe a logical process that is actually inductive summary. It is true that inductive reasoning and analogical reasoning are the extrapolation and expansion of existing knowledge. But we can't confuse the fundamental difference between the two reasoning methods: inductive reasoning is a generalization from individual (special) to general, and analogical reasoning is an extrapolation from one specific object or field to another.
Others think that reasoning has such a category ratio:
The objects of the class have properties a, b, c and d.
A single object of class s has attributes a, b and c.
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Therefore, a single object of class s has attribute d.
This view is also wrong, because it describes a logical process, which is actually deduced by analogy reasoning based on subjective imagination. Deductive reasoning is to deduce the individual (special) from the general, and analogy is to extrapolate from one specific object or field to another. This fundamental difference should not be confused. In the history of natural science development, analogy is a widely used method in scientific discovery, regardless of ancient times, modern times or modern times. The application of analogy develops with the improvement of scientific thinking level. This development is reflected in: from simple to complex, from static to dynamic, from qualitative to quantitative development.
Many scientists in ancient times, in order to understand the nature of a thing, often compare it with known things qualitatively, that is, they have many similar properties, thus inferring that these two things have other similar properties. For example, in order to understand the spread of sound, Song, an ancient Chinese scientist, said in On Qi and Momentum: "The impulse of a thing is like the excitement of its water. ..... Throw a stone into the water, the water will touch the stone, and it will stop with one punch, and its waves will be inferior, and it will not stop until the text is found. It is also embarrassing. " Here, Song compares the sound of knocking objects with the ripples of throwing stones into the water. Since water propagates in a fluctuating way, sound can also propagate in a fluctuating way. It is here that Song used qualitative analogy to infer that sound propagates in the air in the form of waves.
With the development of modern science, people realize that it is not enough to rely on simple static analogy between things and known things. It is necessary to study the quantity of things' attributes, which requires the combination of qualitative analogy and quantitative analogy. For example, Ohm compared the conduction of current with Fourier's heat conduction theorem. In heat conduction, the temperature difference (Δ t), heat (q) and specific heat (c) of an object are covariant, and its mathematical model is: q = cm (Δ t).
Ohm transfers the covariant relationship between heat and temperature difference to current conduction by analogy, and current (I) is equivalent to heat (Q); Voltage (u) is equivalent to temperature difference (Δ t); Conductivity (1/R) is equivalent to heat capacity (cm), and the mathematical model of electrical conduction is: I = u 1/r, in which qualitative analogy and quantitative analogy are combined. The development of natural science needs to use qualitative analogy and quantitative analogy more and more. Generally speaking, qualitative analogy is the premise and condition of quantitative analogy, and quantitative analogy is the development and perfection of qualitative analogy. Scientific development cannot be separated from qualitative research at first. A very effective qualitative research can often point out the direction for the further development of science, and then quantitative research is needed to achieve an accurate understanding of the law.
Because analogy is a unique reasoning method different from deduction or induction, it can play its unique role where induction and deduction are powerless. Why do you say that? This is because induction, deduction and analogy are all methods of reasoning, but they all draw conclusions from known premises, and the conclusions are restricted by premises to varying degrees. However, conclusions are subject to different degrees of preconditions, among which deductive conclusions are the most constrained by preconditions, inductive conclusions are the second, and analogical conclusions are the least constrained by preconditions, so analogy plays the greatest role in scientific exploration.
At the forefront of scientific development, the application of analogy is particularly important because of its strong exploration and scarce information. For example, in 1963, gherman and Zweig independently introduced quarks as the unit of elementary particles. They pointed out that the motion law of elementary particles can be explained by the simple motion and interaction of three different quarks. Because quark hypothesis can correctly predict new observation facts and describe colorful elementary particles with a simple and unified conceptual system, quark theory has strong explanatory power, but quarks have never been detected alone. Can a single quark be observed? How should elementary particle physics be studied for such a basic problem? According to the quark theory model, quarks can be combined in two ways: one is baryon composed of three quarks and three antiquarks, and the other is meson composed of one quark and one antiquark. If one of these baryon or meson particles is crushed in a nuclear collision, a new particle will be formed, but each new particle can only be composed of the original multi-quarks, that is, it contains either three quarks and three antiquarks, or one quark and one antiquark, and there is no quark or antiquark fragment. High-energy physicists notice that quarks are similar to magnetic substances because magnets always have a north pole and a south pole. When we divide a bar magnet into two sections, there will be no isolated N pole or S pole, but two magnets with N pole and S pole respectively, which is exactly the same as when meson fragments are split. These physicists compare quarks with magnetic poles and lead quark theory to a new starting point. Because the fundamental reason why the two poles of a magnet can't be separated is that the magnetism of a magnet is produced by the circular motion of electrons inside an atom, the S pole and the N pole of a magnet are not the "basic units" of a magnet, and there is a deeper "basic structure"-the external form of atomic current. Since quarks are similar to magnets, do quarks also have unknown "basic structures"? Quarks have an inherent basic structure similar to "atomic flow", which is a prediction obtained by analogy and opens up a new way for establishing the basic theory of quarks. Although we don't know what the "basic structure" of quarks is at present, this prediction is of great significance to the future study of physics. Analogy is often used to explain new theories and definitions, which is helpful for discovery. When a new theory has just been put forward, it is necessary to explain the newly proposed theory and definition with familiar theories through analogy, which is the performance of analogy to help discover. For example, in the theory of gas motion, gas molecules are compared to a large group of particles. Assuming that particles obey Newton's law, there is no energy loss in collision. This analogy has played an important role in the historical development of gas behavior theory. The above examples show that the newly proposed theory must be compared with other known theories before it can be explained. In scientific discovery, the role of analogy in helping discovery can not be ignored.
Analogy and simulation experiments are also closely related. The so-called simulation experiment is to use indirect simulation experiment to study according to analogy when the objective conditions are limited and the research object cannot be directly investigated. For example, how life on earth originated has always been a mystery to scientists, because the original state of the origin of life has changed and it is impossible to investigate directly. From 65438 to the early 1950s, Miller designed a simulation experiment of the origin of life by analogy. He added hydrogen, oxygen, carbon, nitrogen and other elements and methane and water in a sealed container to simulate primitive atmospheric environment such as wind, rain, thunder and electricity. A week later, it was found that amino acids such as glucoside and methionine had been formed in the container. Later, someone used ultraviolet light as energy to get amino acids. 1963, Bonan Peruma did the same experiment as Miller with electron beam.
The experiment has formed adenine nucleoside, which is a big step to uncover the mystery of the origin of life. The achievement of these research results fully shows the important role of simulation experiments based on analogy in scientific discovery.
The role of analogy in scientific experiments is that it is a logical method to design new experimental tools. For example, Wilson invented the cloud chamber for observing the trajectory of elementary particles (he won the Nobel Prize of 1927 for this invention), and Grasett invented the Alvarez liquid hydrogen bathtub with the same purpose. Their original designs were all inspired by analogical reasoning.