William of Ockham (c. 1285–1349) is known for cautioning us to a kind of frugality in our explanations. He would advise that, when we are explaining some event, fact, or phenomenon, we should not invoke any more entities than we need to: we shouldn’t, as we might otherwise put it, multiply entities beyond necessity. Ockham’s principle is thus known as the ‘razor’ since it tells us to cut or shave away from our inventory of what’s contained in the world the entities whose existence don’t serve any useful purpose in our explanation of things.
Many have since found the principle a good one to adopt and find it a useful tool to guide us in our theorising about the world. Perhaps one reason they do so is that simpler explanations are more likely to be true: the fewer entities there are in our explanation, the less complicated the explanation is, and the less complicated the explanation is, the fewer ways for it to go wrong. For comparison, consider a watch. One with only ten mechanical parts can only break in ten different ways. However, one with a hundred working parts could break in at least a hundred. So the simpler mechanism is less likely to fail. | |||