A philosophical razor is a rule that cuts out conclusions that have a low probability of being correct. I use the phrase “low probability” because the nature of a philosophical razor is that it is a rule-of-thumb and not a formal principle. Razors are quite common in colloquial debates and often the same razor will be used on both sides of an argument. For example, Occam's Razor is often used in both atheist and theist arguments because each group has its own opinion as to what the ‘simplest’ explanation is. It is important to note that just because a conclusion is cut out by a razor, that does not guarantee that the conclusion is false.
“Plurality should not be posited without necessity.”
Probably the most famous and readily used razor . Often incorrectly understood as the easiest answer to comprehend is often the correct answer. The interpretation used in science is that when two hypotheses both explain a phenomenon equally well, the simpler hypothesis is generally correct. For example, Lorentz deduced that objects in motion experience a phenomenon called Lorentz Contraction. Essentially, if we are at rest trying to measure the length of an object moving very fast, our measurement will be shorter than if we measured the object when it is at rest. Lorentz believed that this had to do with an object's motion relative to a substance called aether. Einstein’s theory of relativity uses the same mathematical equations as Lorentz, however Einstein’s theory did not require an aether to make mathematical sense. Since science has not been able to show any evidence of the existence of an aether, and since both theories explain the phenomenon of Lorentz Contraction equally well, Einstein’s theory was accepted . In essence, an aether was not necessary to explain what was happening, therefore it could be removed. As a syllogism the arguments may look like this:
P1. Observation X
P2. Aether exists
P3. Lorentz Equations explain phenomenon
C. Relativity with regards to aether
P1. Observation X
P2. Lorentz Equations explain phenomenon
C. Relativity with regards to observer
“What cannot be settled with experiment is not worth debating.”
Also known as “Newton's Flaming Laser Sword” . Alder appears to have been heavily influenced by the ideas of Logical Positivism, which is a school of thought that believes only observable evidence and tautological logic have any rational meaning . Alder chose the name for his razor as a tribute to Newton’s evidence based approach to knowledge and with the intent of letting people know that his razor was much more powerful than Occam’s. The overwhelming cutting power of this razor was not lost on Alder who wrote,
“It must also be said that, although one might much admire a genuine Newtonian philosopher if such could [be] found, it would be unwise to invite one to a dinner party. Unwilling to discuss anything unless he understood it to a depth that most people never attain on anything, he would be a notably poor conversationalist. We can safely say that he would have no opinions on religion or politics, and his views on sex would tend either to the very theoretical or to the decidedly empirical, thus more or less ruling out discussion on anything of general interest. Not even Newton was a complete Newtonian, and it may be doubted if life generally offers the luxury of not having an opinion on anything that cannot be reduced to predicate calculus plus certified observation statements. While the Newtonian insistence on ensuring that any statement is testable by observation (or has logical consequences which are so testable) undoubtedly cuts out the crap, it also seems to cut out almost everything else as well. Newton’s Laser Sword should therefore be used very cautiously.”
Hume’s Razor, Sagan Standard, and Hitchen’s Razor
“If the cause, assigned for any effect, be not sufficient to produce it, we must either reject that cause, or add to it such qualities as will give it a just proportion to the effect.”- Hume’s Razor
“Extraordinary claims require extraordinary evidence.”- The Sagan Standard
Both of these statements are regarding the strength of evidence presented to justify a claim . With the exception of quantum physics, the universe operates on a deterministic system of cause and effect. If we were to, for example, send a pioneer space vessel to Kepler-452b and it found a teapot in perfect orbit around the planet that had the engraving “Made in the USA”, there would be a lot of questions. Was someone playing a practical joke? How old is this teapot? How long has it been in orbit? Assuming that every alternative hypothesis was shown to be false and the only remaining hypothesis was that this teapot was made on Earth and it arrived by some means other than this pioneer spacecraft, the events leading to that teapot being there must be extraordinary by Hume’s Razor standards. By the Sagan Standard, we would need to discover those events before we felt confident accepting the conclusion that this teapot did come from Earth by some extraordinary means.
“What can be asserted without evidence can also be dismissed without evidence.”- Hitchens Razor
While the plain text of Hitchens Razor is fairly straightforward, it also implies that when comparing evidence for or against a claim one should side with the most evidence . If there is evidence for some claim X, in order to refute X we either must counter the original evidence or find equal or greater evidence against X.
Popper’s Falsifiability Principle
Scientific claims must be falsifiable.
This is explained in-depth in the article on Scientific Argumentation. Essentially, due to the problem of inductive logic, falsifiability allows us to deductively eliminate competing hypotheses. In another sense, if a claim, X, is so abstract that we cannot ever observe confirmation of X or a falsification of X, it must not serve a practical purpose in the first place. Does there exist a space unicorn that has no interaction with matter and cannot be observed? I can’t prove that false, but it also serves no practical purpose to believe such a claim.
As a principle of parsimony, conversational implications are to be preferred over semantic context for linguistic explanations.
Unlike the other razors, Grice’s has a logical fallacy to go along with it . Another way to interpret the razor is simply to not set up a straw-man fallacy. When in a debate, it is best to respond to what a person meant rather than a literal interpretation of individual words or phrases. I find this often happens when using metaphors to illustrate points, generally when people respond they will often ignore the metaphor and take it to be a literal equivocation.
This list is not comprehensive of all possible razors and, again, they are rules-of-thumb rather than formal tools. Whether a razor should be employed is a matter of the context of the debate at hand, as a razor has very little convincing power. If your goal is to persuade someone of an alternative position, a razor may not be much help. Grice’s razor is the most universal razor as it can apply to any debate, followed by Popper’s which is pivotal to science. While the other razors can be powerful tools, they are best used when evaluating your own beliefs with an open mind rather than convincing someone else that their position has been cut.