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Why are Simpler Explanations Usually Better?


 

Old door and hinge
The purpose of science is to make things simpler and not more complicated. Scientists strive to discover theories and explanations that simplify the view of our world and not complicate them. According to Wiliam of Ockham (c. 1288 – c. 1347), if there are competing explanations for a phenomenon, the simpler explanation is to be preferred. The simpler explanation is often the correct one. It can be summarized as “With all other things being equal the simpler solution is the better one.” Simpler explanations rely on fewer assumptions which can not be proven or disproven.

In this edition of TOK-Talk I would like to explore the difference between a good and a bad explanation. Why are simpler explanations usually the better ones? Listen to find out!

Sometimes I am asked the question, why science is so complicated. I remember that during my studies at university, I also asked my professor the very same question. At that time I was very intrigued by the complexity of the biochemical events that occur in living cells. He laughed, but in a well meaning way, I’d have to add, and responded that everything is complicated only if you hear it for the first time. If you hear something over and over again, then you start to become used to it.

Naturally, I have to admit that many aspects of the sciences are indeed difficult to understand for the “non-initiated”. There are several reasons to it. Many scientific concepts are difficult to imagine and often we are missing suitable analogies to our real-life world. We have a difficulty in drawing parallels. If I tell you, for example, that the DNA, the genetic information in each one of our body cells is over 2m long, then this is difficult to imagine how you can fit so much DNA into one single cell. We simply do not have any real-life comparison. The DNA is just unimaginable thin. Or another example: the total surface area of our lung is about 100m². That’s the area of my apartment. And the total length of all blood vessels in the human body is nearly 100000km. This is 2 and a half times around the earth, or 1/3 of the way to the moon. This is of course difficult to imagine, because we are missing a link to our everyday experience. And let’s not talk about the dimensions in the universe or time scales of billions of years. I claim that not even scientists can imagine these dimensions, but they have learned to at least work with these numbers.

These were now rather subjective perception of complexity in the sciences. But are there are also other criteria. William of Ockham lived in the 13th and 14th century. He was a scholar and an early proponent for the KISS principle: Keep it Short & Simple.

The purpose of science is to make things simpler and not more complicated. Scientists strive to discover theories and explanations that simplify the view of our world and not complicate them. According to Ockham, if there are competing explanations for a phenomenon, the simpler explanation is to be preferred. The simpler explanation is often the correct one. It can be summarized as “With all other things being equal the simpler solution is the better one.”

Please don’t laugh right now, but as you know, I sometimes like to give extreme examples to make my point clear. – I have got a little thermometer here. When I place the thermometer into the sun then the mercury rises. When I put it into the shadow, the mercury drops. Do you know why this happens? There is a little invisible demon inside the glass column. In the sun the demon wakes up and makes the mercury go up. When it’s dark the little critter goes to sleep and the mercury column drops.
During a bright winter day the demon is asleep. It is hibernating and will only wake up in spring. Sometimes the little demon wakes up even during winter and makes the mercury go up a bit…
You see, the little demon is very convenient. We are able to explain every movement of the mercury column with its help. No matter how the mercury moves, it’s the demon’s fault.

We of course know that the temperature is higher in the sun than in the shadow, and that the temperature is responsible for the change in the thermometer. The interesting question is now, if there are any objective criteria that allow us to determine which explanation, the demon or the temperature is a better explanation for the observed change. Why should we disregard the possibility of the little demon right from the start? Why should you give the temperature a higher priority? Over the course of our education, we were taught that thermometers measure temperature, so maybe we are biased into that direction. But let’s try to remain objective.

The explanation with the little demon is indeed a very complicated explanation. We have to take many assumptions. The biggest assumption is that the demon exists in the first place. There is no way to prove or disprove its existence. It is therefore even an unscientific claim. The presence of the demon also generates more questions than it solves. Where does the demon come from? How did it get into the thermometer? Why does it wake up during a bright day? Why does it hibernate? How does the demon interact with the mercury to make it go up and down? And why does it do that? In contrast, The temperature explanation is much simpler – it does not rely on as many unverifyable assumptions. It is thus more probable and more likely to be correct.

The rule for simplicity has become to be known as Ockham’s Razor. You have to shave away all unnecessary assumptions. Why assume the existence of the invisible demon in the first place? We could just as well assume that the mercury itself responds to the light the way it does. This would be a much simpler explanation and it’s also more testable. The invisible demon is just an unnecessary assumption that makes the explanation more complicated than necessary.

But could it, theoretically, not be possible that the simplest explanation is sometimes not the correct explanation? Maybe one theory relies on, say, 5 correct assumptions, and the other theory on one wrong assumption. We just could not test the assumptions yet.

Of course this is possible, this is why Ockham’s Rule states that the simplest explanation is usually the correct one. It’s a good starting point. You see, I you want to you can make any explanation more complicated than necessary. This is easy to do, but what do you gain from that? For some for me unexplainable reason, many people adhere to conspiracy theories. The moon landing never happened; Princess Diana was murdered she did not die in a normal car accident; Elvis lives, and so on. All of these claims generate more questions than they answer and require a whole range of assumptions.
I see that unfortunately time is running out again. And you are all waiting for the closing quote. I chose one from Albert Einstein. I think it fits quite well into the topic. He said: “Make everything as simple as possible, but not simpler“.

Questions for Discussion:

  • Can you come up with examples where the theory or explanation with the fewest assumptions is not always the best explanation?
  • Is it not also important to consider the quality of the underlying assumptions and not just the number of assumptions that carry a theory or hypothesis? How can the quality of assumptions be assessed?
  • Try to collect examples of various conspiracy theories (eg. the moon landing which supposedly never happened, etc.). Try to come up with a list of assumptions that you have to take in order to accept these conspiracy theories.
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Knowledge is a process of piling up facts; wisdom lies in their simplification.

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