POTENTIALLY REFUTABLE HYPOTHESES
Testing if an hypothesis is falsifiable is a basic filter in skeptic reasoning, yet appears to be widely misunderstood. The concept that something has to be falsifiable in order to be validated may indeed come across as paradoxical at first.
Personally I do not like the term “falsify” in this context, because it is too easily misunderstood as to mean “fraudulently alter” and then gets confused with data or evidence tampering. I therefore refer to “potentially refutable” here. Karl Popper (see below), who developed the concept, also often used the term refutable, so I regard it as appropriate.
Even if observations confirm an hypothesis a thousand times, it will still not prove such an hypothesis to
always hold true. Conversely, it would require only one contradictory observation to discredit the hypothesis. The test for universal validity does therefore not rely on positive confirmation, but on potential refutation. If an hypothesis is phrased such that there is no means by which it can be refuted, it becomes impossible to test its validity. Another phrasing used by Popper specifies that it must be “capable of conflicting with possible, or conceivable, observations”. Failing this, an hypothesis is unscientific.
Salient questions to ask would be:
• How would one go about refuting the hypothesis?
• What evidence would be required to refute the hypothesis?
If the answer to these questions is “impossible”, the hypothesis is unscientific.
Popper argues that unscientific theories are not necessarily worthless in that some of them have been shown to evolve into valuable theories in the past. However, it is clear that they are of little worth.
An extract from
Conjectures & Refutations by Karl Popper on this topic is available
here. I recommend reading the whole extract, but here’s a bit:
1. It is easy to obtain confirmations, or verifications, for nearly every theory — if we look for confirmations.
2. Confirmations should count only if they are the result of risky predictions; that is to say, if, unenlightened by the theory in question, we should have expected an event which was incompatible with the theory — an event which would have refuted the theory.
3. Every "good" scientific theory is a prohibition: it forbids certain things to happen. The more a theory forbids, the better it is.
4. A theory which is not refutable by any conceivable event is nonscientific. Irrefutability is not a virtue of a theory (as people often think) but a vice.
5. Every genuine test of a theory is an attempt to falsify it, or to refute it. Testability is falsifiability; but there are degrees of testability: some theories are more testable, more exposed to refutation, than others; they take, as it were, greater risks.
6. Confirming evidence should not count except when it is the result of a genuine test of the theory; and this means that it can be presented as a serious but unsuccessful attempt to falsify the theory. (I now speak in such cases of "corroborating evidence.")
7. Some genuinely testable theories, when found to be false, are still upheld by their admirers — for example by introducing ad hoc some auxiliary assumption, or by reinterpreting the theory ad hoc in such a way that it escapes refutation. Such a procedure is always possible, but it rescues the theory from refutation only at the price of destroying, or at least lowering, its scientific status. (I later described such a rescuing operation as a "conventionalist twist" or a "conventionalist stratagem.")
One can sum up all this by saying that the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.
