As Einstein put it in his Autobiographical notes : " This is an interesting example of the fact that even scholars of audacious spirit and fine instinct can be obstructed in the interpretation of facts by philosophical prejudices. Occam's razor is often cited in stronger forms than Occam intended, as in the following statements.
Notice how the principle has strengthened in these forms which should be more correctly called the law of parsimony , or the rule of simplicity.
To begin with, we used Occam's razor to separate theories that would predict the same result for all experiments. Now we are trying to choose between theories that make different predictions. This is not what Occam intended. Should we not test those predictions instead?
Obviously we should eventually, but suppose we are at an early stage and are not yet ready to do the experiments. We are just looking for guidance in developing a theory. This principle goes back at least as far as Aristotle, who wrote " Nature operates in the shortest way possible.
The principle of simplicity works as a heuristic rule of thumb, but some people quote it as if it were an axiom of physics, which it is not. It can work well in philosophy or particle physics, but less often so in cosmology or psychology, where things usually turn out to be more complicated than you ever expected.
Perhaps a quote from Shakespeare would be more appropriate than Occam's razor: " There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy. Simplicity is subjective and the universe does not always have the same ideas about simplicity as we do. Successful theorists often speak of symmetry and beauty as well as simplicity. In Paul Dirac wrote " The research worker, in his effort to express the fundamental laws of Nature in mathematical form, should strive mainly for mathematical beauty.
It often happens that the requirements of simplicity and beauty are the same, but where they clash the latter must take precedence. The law of parsimony is no substitute for insight, logic and the scientific method. The simpler a hypothesis is, the more easily it can be proven or falsified. A complex explanation for a phenomenon involves many factors which can be difficult to test or lead to issues with the repeatability of an experiment.
As a consequence, the simplest solution which is consistent with the existing data is preferred. However, it is common for new data to allow hypotheses to become more complex over time. Scientists choose to opt for the simplest solution as the current data permits, while remaining open to the possibility of future research allowing for greater complexity.
When you have two competing theories that make exactly the same predictions, the simpler one is better. Obtaining funding for simpler hypotheses tends to be easier, as they are often cheaper to prove. We could still imagine that there is a set of laws that determines events completely for some supernatural being, who could observe the present state of the universe without disturbing it. However, such models of the universe are not of much interest to us mortals.
Making minimal diagnoses reduces the risk of over-treating a patient, causing panic, or causing dangerous interactions between different treatments.
This is of particular importance within the current medical model, where patients are likely to see numerous health specialists and communication between them can be poor. In this context, it refers to the idea that people should be given the least punishment necessary for their crimes. This is to avoid the excessive penal practices which were popular in the past.
For example, a 19 th -century English convict could receive five years of hard labor for stealing a piece of food. The concept of penal parsimony was pioneered by Jeremy Bentham, the founder of utilitarianism.
He held that punishments should not cause more pain than they prevent. Life imprisonment for murder could be seen as justified in that it might prevent a great deal of potential pain, should the perpetrator offend again. Which theory do you choose? This sounds like good sense: Why make things more complicated than they need be? You gain nothing by complicating an explanation without some corresponding increase in its explanatory power.
The worst misuses, however, fixate on the idea that the razor can adjudicate between rival theories. I have found no single instance where it has served this purpose to settle a scientific debate. Worse still, the history of science is often distorted in attempts to argue that it has. In order to get the mistaken geocentric theory to work, ancient philosophers had to embellish circular planetary orbits with smaller circular motions called epicycles.
These could account, for example, for the way the planets sometimes seem, from the perspective of the Earth, to be executing backwards loops along their path. It is often claimed that, by the 16th century, this Ptolemaic model of the universe had become so laden with these epicycles that it was on the point of falling apart.
Then along came the Polish astronomer with his heliocentric universe, and no more epicycles were needed. This is wrong for many reasons. Largely because planetary orbits are in fact elliptical, not circular, he still needed them and other tinkering, such as a slightly off-center Sun to make the scheme work.
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