This article outlines the indisputable truth that evidence does not lead to theoretical truth - that is, despite scientific theories being empirically successful, being supported by evidence, and accepted by the scientific community that does not mean they are true. It starts by looking at how the ‘no-miracles’ thesis leads many to naively conclude that science somehow maps the truth. Then it looks at several examples where scientific theories have been remarkably successful but have later been shown not to be true. It then looks at how evidence for a theory can not prove that a theory is true and conversely how evidence against can not prove a theory is false; and lastly it looks at how falsification (making novel predictions) also does not tell you if a theory is correct or not. It concludes by saying that no matter how much evidence there is for or against a theory that alone can not prove that a theory is correct or not.
NO MIRACLES THESIS
The ‘no-miracles’ thesis makes the intuitive case that the success of science proves that its theories must be true. It makes the case that it would be nothing short of a miracle if the laws of physics could allow technology to work and not map the truth in some very fundamental way. For example, how could Newtons Laws Of Motion (NLOM) be used to fly airplanes, create satellites, and take man safely to the moon and back if they were not true. While this ‘no-miracles’ thesis is intuitive the history of science has shown that a theory can work but still be false.
WORKING VS BEING TRUE
Newton's laws were verified by experiment and observation for over 200 years. Newton's laws of motion, together with his law of universal gravitation and the mathematical techniques of calculus, provided for the first time a unified quantitative explanation for a wide range of physical phenomena and up until 1905 there was no reason to think that the Newtonian theory was not completely true. And although not found in the Principia it was natural for scientists and philosophers to create a world view and in the late in the eighteenth century Laplace posited the “clockwork universe” model which was generally accepted. However, as everyone knows in 1905 Einstein showed that the “clockwork universe” model was incorrect and NLOM were at best an approximation which only apply under certain circumstances. In other words, although NLOM work, they are not true despite it being confirmed for over 200 years and universally accepted by scientists as being true.
It is worth stressing that Newtons laws of Motion were wrong about very fundamental issues and give a completely wrong picture of the world around us. Newton’s theory asserted that space and time are absolute, that there is action at a distance, and that inertial mass is constant: all that and more is wrong with Newton's theory.
EVIDENCE AGAINST DOESN'T MEAN IT’S WRONG
Another intuitive notion is that a theory that has been abandoned by scientists because there was evidence against it can be considered not true. However, the history of science shows us that even theories that look like they are discredited and abandoned can not be ignored. There are many disproved theories in the history of science which later came to be accepted such as the wave theory of light, atomic theories, chemical theories and kinetic theory of heat which were later revived and used today.
One of the many examples of disproved theories that were later resurrected was Prout’s chemical theory. Prout's hypothesis was an attempt to explain the existence of the various chemical elements through a hypothesis regarding the internal structure of the atom. He hypothesized that the hydrogen atom was the only truly fundamental object, which he called protyle, and that the atoms of other elements were actually groupings of various numbers of hydrogen atoms. However, measurements compiled by Jöns Jakob Berzelius disproved the hypothesis although it later became accepted again. Likewise, the Wegenerian theory that the continents are carried by large subterranean objects moving across the earth was refuted by several observations and dismissed by scientists but later became an accepted orthodoxy of science. Yet another example was the refutation of Newton's corpuscular theory of light by Leon Foucault when he measured the speed of light and it was concluded that he had proved that light was a not made of particles which is now again back in fashion.
EVIDENCE FOR DOESN'T MEAN IT’S RIGHT
The number of theories which were supported by evidence and the scientific community but later abandoned are massive and include theoretical entities such as phlogiston, caloric, and a range of ethers among many others. Here is a list of ten theories that were supported by evidence and the scientific community and later abandoned:
Ten theories have been picked for no particular reason and in practice it this list could continue ad nauseam. It is important to understand that each theory was once successful and well-confirmed by the evidence, but which contained central terms that (we now believe) do not refer to anything in reality.
FALSIFICATION DOESN'T MEAN IT’S RIGHT
Naive falsification is an unsuccessful attempt to produce a rationally unavoidable method for science in which it is claimed that scientific theories are proved when they make novel predictions which turn out to be true. However, naive falsification is not a watertight thesis (as Popper recognised) as many theories have been ‘falsified’ in this way which have later been abandoned. For example, Newton's theories of motion had a stunning range of predictive success: the perturbations of the planetary orbits away from strict Keplerian ellipses, the variation of gravity over the earths surface, the return of Halley’s comet, precession of the equinoxes and so on. Furthermore, Newtonians even turned empirical difficulties (like the initially anomalous motion of Uranus) into major successes - the prediction of the hitherto unknown trans-Uranian planet that we now call Neptune. But despite this predictive success it is now believed that Newtons Laws of Motion are untrue. It is worth stressing again that Einstein's work is not an extension of Newtons because the two theories are logically inconsistent: if Einstein’s theory is true then Newton’s is false. Therefore, Newton's theories have considerable predictive success despite being wrong.
Several other theories have shown predictive success but have later been abandoned. For example A. Fresnel used a now abandoned optical theory that included the ether to predict that a certain experiment would create a bright spot at the centre of the shadow of a circular disk. This surprising result was tested and then assumed to be positive evidence that the ether theory was indeed true. In fact, the ether theory made several positive predictions and was well confirmed leading scientists such as J. C. Maxwell to claim that ‘the ether theory was better confirmed than any other theoretical entity of natural philosophy.’
EVIDENCE ISN'T WHAT YOU THINK
Although it could be claimed that the development of science is cummulititive at the empirical level (it is able to be more predictive) at the theoretical level we must conclude that even our best and most successful theories are at best dubious and at worst totally wrong. It must be accepted that the history of science makes it very unlikely that our present theories are even approximately true and our current theories are probably wrong. This led Professor Arthur Fine to conclude:
"Realism [the belief that science is true] is dead. Its death was announced by the neo-positivists, who realised that they could accept all the results of science, including all the members of the scientific zoo, and still declare that the questions raised by the existence claims of realism were mere pseudo-questions. Its death was hastened by the debates over the interpretation of quantum theory, where Bohr’s non-realist philosophy was seen to win over Einsteins passionate realism."
It could well be that science is the best way to accumulate knowledge that we have and ever will have. Even if we accept this we must admit that there are practical limits on our knowledge and there are limits to the very intuitive common sense notion that evidence entails truth.
We must also conclude that simplistic models of science are too simplistic and not useful. For example, the idea that a theory is true once it has been falsified (novel predictions that have been confirmed) is simply wrong. We must also admit that a theory is not true because there is some evidence for it. In fact, we can not even know a theory is correct even when it has a lot of evidence for it. We must also admit that we can not show a theory is wrong when there is evidence against it.