Dan had a comment on the “science and proof II” posting that I think is of general interest that requires a fresh posting. He asks:

“Okay, do you have a quick explanation for why falsification is not the distinction between science and religion?

On a day to day level, it works for me. If someone says there exist leprechauns, but they are invisible, and leave no trace in our world, I know that the statement can not be proven wrong so it is not worth arguing against. But if someone says that species evolve from other species, it is conceivable that it could be proven wrong, so it is worth taking seriously. And if enough people try to disprove it and fail, that is good evidence that it might have explanatory power.”

Dan’s point is a good one. At a simple level, falsificationism sounds plausible. The theory that “All swans are white” can be seemingly falsified by the appearance of aa single black swan. Falsification’s appeal stems from the fact that we seem to be able to make a clean distinction between an observation and a theory.

But that distinction becomes blurred when you start looking at the kinds of things that scientists research, because then observations are no longer simple sensory perceptions. The statement “electrons exist” is not a simple observational one but requires us to use a vast array of theories from a range of disciplines in order to interpret the readings of the measuring insruments. So if the “observation” disagrees with the theory being examined, it is not clear where to place the blame. Is it on the theory being tested, or on one of the theories underlying the observations?

So in reality one is always comparing one set of theories with another set of theories and there is no rule that *forces* you to make a particular choice, although good taste and judgment and standard practices may lead the scientific community to a consensus decision.

The other problem with using falsification is that no theory has ever explained everything in its domain. There are always unsolved problems and contradictory results. Trying to reconcile these discrepancies serve as the basis for much research. If we applied the falsification rule strictly, then every theory we have would be falsified.

These are the kinds of things that caused falsificationism to stumble and fall.

Incidentally, even the swan example is not as simple as it looks. Defenders of the white swan theory can retain their belief by arguing that what constitutes a swan is not precisely defined and that the black creature was not really a swan, and other arguments like that. We may dismiss those arguments as silly and self-serving but they are not logically ruled out.

Warning! Shameless plug coming up!

All these issues are discussed in my book “Quest for Truth: Scientific Progress and Religious Beliefs”, published by Phi Delta Kappan Foundation in 2000.

In his comment on my earlier posting on “Science and Proof”, Kurtiss Hare raises an interesting point about the value of religion and what kind of validity criteria I was referring to, so I thought I would elaborate.

When it comes to the *value* of belief structures to an individual, then there are really no external criteria that can be imposed. For example, for someone who has experienced a personal tragedy, a belief in God and a divine purpose for life may be of far more value than all the science in the world.

The point I was trying to muddle through to about science is that it is not being “proven true” that gives scientific theories their credibility, but the fact that they seem to work well, are reliable, and can be used to make predictions.

The probability argument that Kurtiss raises is interesting but has two directions in which it can be taken. The first (which I think is the one he makes) is that the fact that very few planes crash means that the probability of that particular application of the scientific theories (i.e., arriving safely) is high.

But does that translate into a high probability of the underlying scientific theories being true? No, because if you you want to assign a “truth probability” to a scientific theory then you have to compare (for any given theory) the number of predictions that are confirmed to the total number of predictions that are conceivable. Since for any non-trivial theory the number of possible predictions is infinite, the truth probability for *any* theory (however “good”) turns out to be zero!

This seems paradoxical but philosophers of science have not been able to get around it.

On a plane earlier this week, I was seated next to a very nice woman and we struck up a conversation that quickly turned to religion. She was a Biblical literalist who belonged to an evangelical Christian church. In the course of comparing the scientific and religious approaches to describing the world, she made the claim that the theories of evolution and the big bang had not been “proven” and that thus they were articles of faith, just like any religious dogma.

This is a familiar argument to anyone (like me) who has been involved in the whole brou-ha-ha about whether “intelligent design” should be taught alongside Darwinian natural selection in science classes, and it reveals a common misperception about the nature of science.

This view is not held just by religious people, it is widespread. In the first class in my course on the history and philosophy of science, I ask students how they would distinguish science from non-science and invariably they begin by saying that science consists of things that have been proven true.

But nothing, even the most robust of theories, is “proven to be true” in science. But does that mean they are pure articles of faith, on a par with religious beliefs? Surely not. Newton’s laws and the laws of hydrodynamics have not been proven true either, but the woman and I both boarded the airplane confident that the those laws would hold and that we had a very high chance of arriving safely at our destination. Are there any religious beliefs to which we would trust our lives as confidently?

Clearly, the fact that the laws of science are not proven true does not diminish their worth and validity. Thus their credibility must be based on something other than simple proof. But most teaching of science, at any level, pays little attention to this important feature of scientific knowledge. And so the public policy discussions on issues like intelligent design rarely get beyond a fairly simplistic level.

Too bad.