What distinguishes science from pseudoscience? In my experience, if you ask a practicing scientist this question they will likely answer:
“We have logic on our side! Proper scientific theories can be falsified, while pseudoscientific theories cannot.”
You might remember Dr. Ng bringing this up in the first lecture on climate change in January. At the same time, I was reading an essay written by Karl Popper, the father “falsification” as we now know it, for a grad course I’m currently enrolled in.
So, what is falsification?
Here’s the gist*. There are inductive and deductive logical assertions. Inductive assertions involve some sort of non-guarantee, while deductive assertions provide a guarantee. The most intuitive form of inductive logic takes the form of enumerative induction, or:
Every piece of paper I have seen has been white.
- Therefore, the next piece of paper I see will be white
- Therefore, all pieces of paper are white
Deductive logic takes a different form, and follows a number of deductive rules. Here is the rule, modus ponens:
- If p, then q
- therefore, q
Of course, q must only be so insomuch as the prior requirements of q are met fully (i.e. that p was so).
I think the difference between deductive and inductive logic is fairly intuitive. The natural question that arises, then, is, “Does science deal with inductive, deductive, or both forms of logic?”
Lets think about this question for a moment: does science concern itself with non-guarantees? I think the answer is obvious. Yes. The scientific method is founded on non-guarantees, after all. Hypotheses are by their very nature not guaranteed – or are they?
David Hume, a renown 18th century British skeptic and philosopher first formulated the Problem of Induction (POI) into how we know it today. The POI can be set up and described as follows:
- Scientific theories are not only concerned with describing past events, but also with predicting future occurrences of events
- In order to move beyond particular observations (i.e. this piece of paper is white) to generalized assertions (all pieces of paper are white), one must use inductive logic, since it it irrational to assume the universe possess any notion of regularity (that is, it is irrational without having observed the entire universe and all occurrences of paper throughout time).
- Therefore, one must somehow be guided by a principle, whose tenets successfully allow one to rationally make use of inductive assertions (i.e. hypotheses)
- But what form of logic must this principle take? It cannot be deductive, as it would then cease to be inductive.
- It cannot be inductive, as that would require one of two things: an infinite regress of higher order principles to rationally justify the next lower principle (Popper); or the use of circular logic (one cannot use an inductive rule to justify inductive logic)
- Since any justification must use either inductive of deductive logic, a principle cannot be rationally justified. This is the POI.
Popper thought he had a nice and tidy remedy for the problem of induction: get rid of it entirely, and adopt deduction as the sole basis for scientific inquiry and progress (i.e. since induction cannot be used rationally, get rid of it and figure out a way to deal with the fall out). Popper then utilized falsification: the notion that there must always exist the possibility that a true counter example for every hypothesis exists. Therefore, if one were to test a hypothesis and observe the counter example, one would have deductively falsified the hypothesis of interest.
Naturally, one may then ask, “What happens when you fail to falsify a hypothesis? Is the hypothesis then confirmed?” According to Popper, no, since doing so would implicitly make use of inductive assertions (since one can never prove a theory to be true without having observed all possible cases where it is being tested).
“Popper, you’re a mad man!” you might say, “How can you possibly confirm a hypothesis without using inductive logic?”
The “Popperian science” consists of the following: “bold conjectures” and concomitant refutations. Popper thought he could do way with the POI by requiring science to make use of some serious fire power when it came to coming up with hypotheses, nothing that could be knocked down by a philosophical breeze. After rigorous testing and verification, via internal (is it internally consistent? is it consistent with the rest of science?), and external tests (can you formulate something meaningful with the theory, and then test it in the real world).
If a theory held up to the most scrupulous eye, it was deemed corroborated. This is the equivalent to a time log of all the instances where the theory was not falsified and, as Popper maintained, contains no shred of confirmation, nor implications regarding the likeliness a given hypothesis will be true in the future.
Sounds strangely like induction, doesn’t it?
- Coming up:
- Part 2: Objections to Popperian Falsification
*Note: I am neither a philosopher, nor a philosophy graduate student. I simply find this stuff fascinating. If you take offense to anything in the above article and feel obliged to correct me in the comments field, please do so with the most honorable intentions in mind. Crushing my spirit will do neither of us good (unless you sustain on spirit juice, perhaps muddled with some lime and fresh mint. In that case, I can’t really say no, can I?).