Arguments for Realism

If someone claims to be a realist he might be asked why he is one. This question may have two meanings. It might ask for an explanation: How come? What hap­pened to you that you became a realist? Are there causes which made you a realist? Was it an episode, an insight, a special discovery, an accident? Did something change your opinion or did you just realize that you had been a realist before and became conscious of your own opinion only now? Without striving for com­pleteness we shall collect some possible answers to these causal questions.

E1 Psychological evidence

There is psychological evidence suggesting, even forcing us to take things we see or hear or feel for real. Although we know that we might be wrong, this kind of psychological evidence is very strong, and it is very difficult to overcome it even if there are rational reasons against it.

E2 Realism is rooted in our language

More often than not things with a name are taken as real. This can be seen clearly in languages with a definite article „the“—Greek, German, English, and even Romance languages (but not Latin!)—where things with a definite article seem to be concrete, even tangible, hence real.

Since the realistic weight of our senses and of language are so strong we nor­mally do not doubt what they teach us. Thus under normal conditions the burden of proof is not with the natural realistic position, but with the sceptical side. For most people, especially for children, it is much easier to trust than to doubt.

E3 Realism is rooted in our perceiving and handling the world

The reason is simple: In evolution it paid to be a realist. Doubting and investigating takes time, and if you prefer to check whether something looking like a tiger is really a tiger, you might not survive and not bring your sceptical genes into the next generation.

Up to now we asked for the causes of realistic thinking. But the question „Why are you a realist?“ might also go in another direction: It may not ask for historical events or for evolutionary explanations, but for arguments: Are there good reasons to be a realist? Are you logically entitled to be a realist? Could your reasons be good enough not to persuade people but to convince them? In what follows we shall try to answer these questions. And we shall number our answers by A for „Argument“. But let it be clear from the start that there is no final argument proving that realism is right. That makes the case more difficult, but also more interesting.

A1 Simplicity

As we saw, the realistic position is simpler than any other competing position because we are born as realists. This fact alone however does not mean that realism must be right. But it is easier to handle.

This leads to another advantage:

A2 Simple theories, if wrong, are easier exposed as wrong

If the realistic position is wrong then it should be easier to be recognized as wrong than positions which are more complicated and can be adjusted by playing with open parameters. According to Karl Popper (1902-1994) we should prefer simple theories against more complicated ones because with simpler candidates we have better chances to find out what is wrong with them. And knowing this we will have more motivation to search for better theories.

A3 Which kind of realism ?

There are many positions between pure solipsism (I am the only thing existing) and naive realism (the world is just as it seems to be). If we had to choose we would start with extremes. One extreme is solipsism. Although not strictly refutable, it is no serious choice. The other extreme—naive realism—is easily refuted. In order to make a tenable choice, we suggest to choose a position as realistic as possible, that is compatible with our factual knowledge.

Why so cautious? Quantum mechanics is a very successful physical theory without a serious competitor, However, up to now not all problems with its interpretation are solved. It seems that on the microscopic level the concept of realism must be refined. Meanwhile the strategy for a useful concept of realism will be: „let's be as realistic as possible".

A4 Convergent functions of sense organs in organismic systems

Simple example: There is a drinking-cup. We can see it and feel it (and sometimes —alas—even hear it). This convergence of our perceptions is simply explained by the hypothesis that there is just one real object: a cup.

A5 Constancy achievements, especially of perception (in German „ Konstanzleistungen “)

An example: Eye and brain inform my consciousness that a moving object moves. If the object is not moved, but my head is, then the brain tells this to my con­sciousness, although the signal reaching my retina moves! Such constancy achievements work in all higher organs concerning colors, forms, depth, direction, objects. They make sense only if there are indeed real objects.

A6 Invariants in science

Many things, if not all things, change. But there are some properties which do not change. We call them constants of nature or even laws of nature. There are con­servation laws saying that energy, momentum, angular momentum, electric charge, and others, are constant. This suggests that there must be something outside us and not depending on our existence, our thoughts, our wishes, ideas, views, points of view, preferences, or even our actions. There are things or relations we may find and measure, but not change. Something real, even something objective.

A7 Convergence of different measuring methods

Many things in science may be measured. Sometimes the results depend on the methods we use for measuring. But very often it is possible to use different methods of measuring, but to find the same values.

A8 Convergence of measuring results

If scientists measure a special quantity, for instance the speed of light, they should lay open the precision of their results and try to improve them. In fact, if we follow the history of scientific research, we see that measurements got better and better and that the limits of possible mistakes get narrower. In this case we may even say that the values converge against an asymptote in the mathematical sense—even if the possible error is never zero. (There are no infinitely exact measurements.) This kind of convergence also suggests that there is a true value, a real value of a real property.

A9 Convergence of theories

Sometimes two or more theories compete with each other. It may happen that they start from different premises, but still deliver the same testable results. They might even contradict each other in their premises, but still lead to the same testable predictions. Thus we might fear that to every accepted theory there are competitors. We could not tell then which theory is true because all of them would (not be proven, but) confirmed by our empirical tests. Hence we could not decide how the hidden reality is structured. This would be an unpleasant situation for scientists, for teachers, for all curious people.

But the normal situation is different. As Albert Einstein remarked 1918 in his Planck lecture Principles of research: „The development of physics has shown that of all conceivable constructions always a single one has proved itself uncondi­tionally superior to all others.“ If only one theory survives, then it is legitimate and usual to suppose that we have uncovered part of reality.

True, there are cases where there is not such a final decision between true and false. The best example is quantum physics where there are two theories accepted: Heisenberg’s discrete matrix approach of 1925 and Schrodinger’s continuous dif­ferential equation of 1926. But in this case it turned out (and was proven by Schrodinger himself) that both approaches are empirically equivalent. They can be regarded as the same theory in different clothes. There is a difference in the pre­sentation, but no contradiction.

A10 Increasing coherence of theories

In addition, scientists sometimes succeed in formulating more general theories, to combine two or more theories to one overarching theory. This is also a hint to the existence and uniqueness of reality. Isaac Newton (1643-1727) formulated his law of gravitation for the astronomical objects known at his time. Later it turned out that they apply also to meteorites, moons, stars, double stars, star clusters, „nebulae", galaxies, clusters of galaxies, even to the universe. And James Clerk Maxwell (1831-1879) discovered that electricity, magnetism and light can be described by one theory, formulated in the so-called Maxwell equations.

Scientists try to formulate even more general descriptions of the world. Whether there is a World Equation or a Theory of Everything (ToE) describing the funda­mental principles of the whole world, and whether it can be found by us, is not known. It is clear however that, even if it exists and can be found, it will be very abstract. But it would still yield a further argument for the existence and uniqueness of a real world.

A11 Growing objectivity of scientific worldview

For hundreds and thousands of years, philosophers have discussed, which parts of our knowledge are objective and which are contributed by the knowing subject, hence subjective. We don't claim to have a final answer to this question, but we are convinced that we have made progress. As an example we take light: Colours are subjective, wavelengths are objective.

Science has not only discovered new things and new facts, but has also made progress in questions of objectivity. With these results science has also brought more objectivity in our worldview.

A12 Success of realistic theories:

In the very beginning of our paper we cite Putnam with his bon mot „Idealism makes the success of science a miracle", and also van Fraassen talking about the success of science as the „Ultimate Argument for realism". In both cases the success of science is claimed to deliver the best argument. We don't criticize that success is used as an argument. In fact, it is just normal that we prefer to rely on things which we know to have worked already. What we criticize is the fact that they took the success of realistic theories as the best argument for realism.

True, Putnam himself later changed his mind and invented „internal" realism in 1982; but in 1994 he preferred to propagate „direct" realism giving its due to immediate experience or even to naive realism. So if you refer to Putnam in an argument you should tell which Putnam you are referring to. For the moment, we refer to Putnam the realist of 1976.

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