Occam's Razor | The Clear and Simple Version

Occam's Razor, so called because it is used to shave off the unnecessary components of an argument, is one of the most basic and important philosophical and logical concepts to understand if one is interested in either field.

However, it tends to get very boring. The purpose of this guide, therefore, is to make it less boring and easier to understand. You never know, you might even have a little fun along the way.

Try not to cut yourself.

• Occam's Razor is a logical principle that states that the simplest explanation for a phenomenon (that is, the explanation that involves the fewest entities) should be considered correct until proven otherwise.
  
  
• It is based on the idea that, when all other things are equal, a simple theory is better than a complex one.
  
  
• William of Ockham is usually credited with first positing the idea, phrasing it: 'It is futile to do with more things that which can be done with fewer.'
  
  
• Though it was originally intended as an argument for the existence of God, it is now more usually used as an argument against it.

Who, Where, When?

William of Ockham was an early Franciscan friar from the town of Ockham, Surrey (in England) who lived from about 1287-1347 CE, making him a philosopher of the High Medieval period, alongside such possibly more famous names as Thomas Aquinus and Francis of Assisi.

Besides having a logical principal named after him, he wrote extensively on physics, logic and theology. His most famous (and important) work in the field of philosophy was Summa Logicae, which for those who's Latin is a little rusty means 'Sum of Logic'. For anyone interested in logic theory, it is a very good place to start.

Question: Why is it called Occam's Razor, when he was from Ockham? Why change the spelling?

• Answer: Good question! Probably because it was the High Medieval period, and everyone's spelling was atrocious. Or possibly, just the spelling of the philosophers and scientists that came after him.

Examples of Occam's Razor at Work

How does Occam's Razor apply itself to reason in everyday situations? Here are a few common examples of how (and why) the principle works to begin with.

You can't find your keys. Do you assume that:

a) You are misremembering where you put them, or

b) Goblins stole them.

I am going to assume that you assume 'a' - this is, without knowing it, applying the principle of Occam's Razor. In the first instance, the solution only requires one entity - you - to be involved. The second involves the interference of another entity, which makes it more complex and therefore less likely without debating the existence or non-existence of key-thieving goblins. The same principle applies when you go to blame someone else for moving them - to comply with the principle of the least complex explanation, you must assume that you have misplaced your keys until it is disproven. Then you can blame other people.

To take the principle further, it is generally to be assumed when speaking logically that the speaker intends the least complex interpretation to be made of their words. That is to say, when someone making a logical argument says something about his mother, it is generally assumed, when adhering to this principle, that he means the woman who gave birth to him, since this is the interpretation that involves the fewest number of entities to come to the result.

Clear as mud? Good.

A famous objection to the principle of Occam's razor is called Hickam's dictum (anyone who says logicians don't have a sense of humour has clearly not been paying attention). It originated in the medical profession as late as the 1950s, and states quite simply that patients can have as many illnesses as they like. The example cited for this objection is the trio of medical problems known as Saint's triad, which often occur together, but at the time were thought to have no connection to each other, thus rendering Occam's razor useless in their diagnosis.

• A point that should be added, though, is that all three complaints in Saint's triad are connected to obesity, the thinking on which has since changed. So, Occam's razor is probably still the one to go with.