In order to refute Aristotle's theory that free fall speed depends on the quality of the object, Galileo told a simple thought experiment. According to Aristotle, if a light object is tied to a heavy object and then dropped from the tower, the heavy object falls fast and the rope between the two objects is straightened. At this moment, the light object will have a resistance to the heavy one, which will make the falling speed slow. However, on the other hand, the mass of two objects tied together should be greater than that of any single object, and the entire system should fall faster. This contradiction proved Aristotle was wrong. Regardless of the resistance of the air, the speed of all free falls is the same no matter how heavy the matter is.
In the confrontation between old and new theories, science has been continuously progressed. New theories were proved to be truth and the old theories were abandoned. So what is the standard of truth? The ultimate standard of truth is practice, but at the same time there are some alternative standards, including prediction, stability, simpleness and logical unified.
Practical standards mean that theory should be able to guide practice so as to realize people's interests. So the practical standard is pragmatism. Practicality means improving people's interests and social progress. People's interests include the interest of oneself and the others, immediate interests and long-term interests. Newton's theorem can be accepted by everyone, mainly because it is conducive to social practice and played an important role in the industrial revolution.
The interests of man are the criteria for testing truth. Strictly, it should be the experience of interest, that is, I feel I have benefit or suffered, I feel uncomfortable after eating a crab, I feel this car is very good, and so on. So the standard for testing truth is direct experience. No matter how much the engineer said about many high-tech used in a car, it does not fully explain the problem, the ultimate test of truth is the user's feeling. Misunder- standings can cause pain, misdiagnosis by doctors, mis- judgment by judges, mistakes in markets, battlefields, and government decisions can all make people feel pain.
Why should we pursue objective truth? Because countless experiences tell us that objective truth is in our long-term interest. The ultimate essence of all the objective truths we speak of are practical truths. Objectivity is not the ultimate goal of understanding, it is just a means. Deng Xiaoping said, “It doesn't matter whether a cat is black or white as long as it catches mice.” Feyerabend's famous saying is “Anything goes.” There is no absolute right or wrong even between science and religion. Feyerabend makes sense, but it is wrong to say “Anything goes.” It is wrong to do against the funda- mental interests of the people, and history cannot be reversed. The ultimate criterion for truth is individua- lism, humanism, and evolutionism. Moreover, the objecti- vity of truth cannot be fully confirmed. All truths must be subjective. Any truth may be overturned in the future. We can only improve the objectivity of the knowledge through practice. That is, the standard of objectivity is the practical standard.
Practicality is the fundamental standard of truth, but this standard is often not easy to use. It is difficult to make timely and accurate assessments of the long-term benefits of people and social progress. To determine which theory is practical, some alternative criteria are needed. Predictability is not only in the interest of people, but also in accordance with the principle of evolution. It is the main difference between science, art, and religion. Therefore, predictability is a substitute standard of truth.
One hundred successful explanations are not as good as a successful prediction. Galileo predicted that objects of different qualities fall at the same speed and it was confirmed by experiments on the Leaning Tower of Pisa. This successful prediction overthrew Aristotle's theory. Einstein opposed the Newtonian system by using the theory of relativity. At the beginning, no one believe it. In May 1919, Eddington's observation of solar eclipse found that the light did bend in the gravitational field. This new experience immediately convinced everyone of Einstein's theory.
Predictability does not confirm a theory. One or two successful predictions may be lucky like a blind cat encounter a dead rat, even many successful predictions do not indicate that a theory can always succeed. Proof of truth is often not accomplished in one go, especially for those important truths and long-term careers that often require constant reflection and verification. No standard tells us how many success can confirm a truth. It depends entirely on people's choices with comparison of different theories.
After an error occurs in the theory, it will not necessarily be immediately overturned, it can often be repaired. But the need for repair means that the theory is unstable. If a theory always changes, it will be hard to convince people. The viewpoint of movement is of course correct, but the idea of static metaphysics cannot be completely denied, because theory must have stability, and it is best to use eternal, universal truth. Even if the theory is not so stable, it should be as stable as possible and should not change every day. When an experimental phenomenon is confirmed in many people's experiments, it is relatively stable and we treat it as truth.
The original meaning of metaphysics refers to abstract theories and was later regarded by Marxism as a static, isolated, one-sided theory that is opposed to dialectics. But this idea of Marxism is wrong because people study abstract theories in order to seek constant things among changes. Therefore, the idea of being static is not a reactionary point of view, but an indispensable point of view required by practice.
Predictability and stability all require time to verify. When the theory is presented, you need some alternative standards to verify immediately. The logically unified theory is the most stable and predictable, so the logically unified theory is the truth. Galileo's thought experiments show that Aristotle's theory is illogical. The only logically unified theory is that the rates of all free falls are the same. The logical thoroughness of philosophy is much better than that of general theories. The mission of philosophy is to realize the logical unification of all theories and to build the entire theoretical building into a completely self-contained system.
The fourth alternative standard of truth is the principle of simplicity, because simple theory is easy to guide practice. People's thinking ability is limited, and although people can use complex theory to get their goals, it is easy to make mistakes. Occam stated: “Every thing that can be achieved with less means does not require more means.” “If it is not necessary, it should not increase the number of real things.” This proposition is the famous Occam's razor. But it should be written in the scientific language: Simplicity is the standard of truth.
Occam's razor once judged religion to be unscientific. In some areas, religion is more successful than science, but religious interpretation depends on God's will,which is complex and changeable. Therefore, religious predictions often make mistakes. It cannot meet people's needs and it is not conducive to social progress. This is the real reason why Occam's razor shaves religion. The standard of simplicity is equal to the standard of practice.
The premise of the choice of simple theory is that both theories can explain and predict the same phenomenon. If the interpretation and prediction of the simple theory is inferior to complex theory, then the complex theory must be chosen.
Based on the previous discussion, we can get the final conclusion of the truth test method.
Trilogy Theorem of Truth Test: The subject for testing truth is each individual person. Practicality is the ultimate criterion for testing truth. The process of testing truth consists of three stages: 1. Verify the logical unity and simplicity of the hypothesis; 2. Verify the stability of the hypothesis; 3. Verify the predictability of the hypothesis.