# Science Series – Part 2: Continuity of Nature

*This is Part 2 of a 5-part series that I am writing on science and PT practice. If you have not read Part 1, do that first before reading any further…*

So René Descartes really tied our hands here. He effectively took away all deduction (except mathematics and logic) and left us with imperfect induction. What does this mean?

In critical thinking, we have deductive reasoning and inductive reasoning. Deductive reasoning is when you start with a premise that is 100% certain and build your argument from there. Inductive reasoning is when you start with an assumption to build your argument. The more likely that assumption is true, the stronger the induction, but you cannot say anything with 100% certainty. The problem is amplified when people use induction to conclude one premise, and then use that premise to build a new induction. The more that you do this, the weaker the induction becomes. Also, no matter how strong your inductive reasoning, you can never be 100% sure that you have anything amounting to real knowledge or truth. This is known as “The Problem of Induction”. How can we know anything with any kind of certainty?

Monty Python has a great example of induction in their famous witch scene from *The Holy Grail*. I’ll supply the synopsis below, but if you have five minutes, watch the clip for yourself – it’s worth it.

The villagers have a woman that they suspect is a witch and would like to burn her (as villagers like to do). They bring her to Sir Bedevere who is a “man of science” for an objective decision. Here is his “scientific” argument.

Witches burn.

Wood burns.

Therefore, a witch must be made of wood.

Wood floats.

Ducks float.

Therefore wood must weigh the same as a duck.

If a woman weighs the same as a duck, then she must be made of wood.

If she is made of wood, then she must be a witch.

Therefore, if a woman weighs the same as a duck, she must be a witch.

Now obviously there are many unsound conclusions and logical fallacies committed here, but you can see how simple inductions can lead to quite absurd conclusions, especially if it “sounds right”. Now, I’m not going to go into depth on validity of arguments and logical fallacies here, it is not the point of this series. If you would like to learn all about that, why don’t you take *Critical Reasoning for Beginners* at Oxford University? Did I mention that it is free, online, only 7 hours in total length, and can be downloaded to your iPod?

So maybe we can try to give some guidance to induction to give us a little more substance. Here is where the Scottish philosopher David Hume comes in. In the 1700s, he made one of the first more effective attempts to tackle the Problem of Induction. What he points out is what is known as The Continuity of Nature. In a nutshell, we can observe natural occurrences and look for patterns. If we find that these patterns have always occurred, we can assume that they will continue to occur. He was quick to point out that this will fail to determine causation, but at least you can define continuity. From here you can make more accurate predictions about future outcomes.

Definitely the underpinnings of science but there are still holes. The continuity is still based on assumptions with no real certainty. Great way to develop hypotheses, but we still have no concrete knowledge. Also we still have the problem of basing future premises on these assumptions, weakening our certainty even greater. Better than Sir Bedevere, but not by much. It is still susceptible to circular reasoning.

Induction gives us only ideas, no reality. We need a better definition. We need a better way of verifying ideas.

Continue to the next post, *Part 3: What is Ockham’s Razor?*