Falsifiability

Falsifiability is the ability of a hypothesis to be tested (verified or falsified) by experiment or observation. It provides us with a spectrum of the reliability of knowledge:
 * Ideas that are falsifiable but not falsified are capable of being tested, have been tested, and have passed the test. They are the most reliable form of scientific knowledge;
 * Ideas that are unfalsifiable are ideas that are not capable of being tested. They may or may not be true, but since there is no way to test them, they are not a reliable form of knowledge;
 * Ideas that are false are ideas that are capable of being tested, have been tested, and have failed the test.

Thus, the purpose of science is to devise experiments which bring ideas out of the ambiguous realm of the "Unfalsifiable," to be classified as either "falsifiable but not falsified" (to be tentatively accepted as true) or "false" (To be rejected).

The important thing to note here is that an idea's being unfalsifiable does not mean that it is false. It means it may be true or may be false, but it simply cannot yet be tested. Thus it is a non sequitur and self-contradictory to argue that "Because an idea is unfalsifiable, it is false."

History of Falsifiability
Evolutionists often mistakenly credit Karl Popper with devising the concept of falsifiability. Actually, the idea was articulated earlier by G.K. Chesterton, a creationist and author, in 1925, while Popper was still studying for his PhD, and nine years before Popper wrote Logik der Forschung.

Science is weak about these prehistoric things in a way that has hardly been noticed. The science whose modern marvels we all admire succeeds by incessantly adding to its data. In all practical inventions, in most natural discoveries, it can always increase evidence by experiment. But it cannot experiment in making men; or even in watching to see what the first men make. An inventor can advance step by step in the construction of an aeroplane, even if he is only experimenting with sticks and scraps of metal in his own back-yard. But he cannot watch the Missing Link evolving in his own back-yard. If he has made a mistake in his calculations, the aeroplane will correct it by crashing to the ground. But if he has made a mistake about the arboreal habitat of his ancestor, he cannot see his arboreal ancestor falling off the tree. He cannot keep a cave-man like a cat in the back-yard and watch him to see whether he does really practice cannibalism or carry off his mate on the principles of marriage by capture. He cannot keep a tribe of primitive men like a pack of hounds and notice how far they are influenced by the herd instinct. If he sees a particular bird behave in a particular way, he can get other birds and see if they behave in that way; but if he finds a skull, or the scrap of a skull, in the hollow of a hill, he cannot multiply it into a vision of the valley of dry bones. In dealing with a past that has almost entirely perished, he can only go by evidence and not by experiment. And there is hardly enough evidence to be even evidential. Thus while most science moves in a sort of curve, being constantly corrected by new evidence, this science flies off into space in a straight line uncorrected by anything. But the habit of forming conclusions, as they can really be formed in more fruitful fields, is so fixed in the scientific mind that it cannot resist talking like this. It talks about the idea suggested by one scrap of bone as if it were something like the aeroplane which is constructed at last out of whole scrapheaps of scraps of metal. The trouble with the professor of the prehistoric is that he cannot scrap his scrap. The marvellous and triumphant aeroplane is made out of a hundred mistakes. The student of origins can only make one mistake and stick to it." G.K. Chesterton, Everlasting Man, II

Despite the obvious philosophical usefulness of a functional definition of falsifiability, many prominent evolutionists regularly misuse the concept in obvious and self-contradictory ways (see Logical fallacy).

As Quinn, a philosopher of science and evolutionist, wrote: In a recent collection of essays, Stephen Jay Gould claims that ' "scientific creationism" is a self-contradictory nonsense phrase precisely because it cannot be falsified'. . Ironically, in the next sentence Gould goes on to contradict himself by asserting that 'the individual claims are easy enough to refute with a bit of research.'. . Since they are easily refuted by research, they are after all falsifiable and, hence, testable. This glaring inconsistency is the tip-off to the fact that talk about testability and falsifiability functions as verbal abuse and not as a serious argument in Gould's anti-creationist polemics. (P. Quinn, "The Philosopher of Science as Expert Witness, " in *J. Gushing, et. al. (ad.), Science and Reality: Recent Work in the Philosophy of Science (1984), p. 43)

Defining the term
There are two more subtle alternative definitions of "Falsifiable," and much of the debate between creationists and evolutionists revolves around these definitions.
 * Ideas are falsifiable when there is some conceivable experiment to test them, but the test may or may not be possible today. This was the view of Karl Popper;
 * Ideas are falsifiable when there is some experiment which can be conducted under present scientific knowledge to test them.

Falsifiability as requiring a conceivable experiment
This definition, while most widespread, is a conceptual failure. If we adopt the first definition, an idea is falsifiable if some conceivable experiment could test it, then we run into a major problem: Which experiments are conceivable?

First, if the history of science has shown anything, it's that scientists are capable of devising new and ingenious experiments to test ideas. For thousands of years, the Greek and Pagan geocentric Ptolemaic system was adopted by the Church as truth, until Copernicus and Galileo found means to test it. An experiment may be inconceivable one day and conceivable the next. The only difference is the presence of a scientist to conceive of a new experiment to solve the problem.

Second, the ability to conceive is a very subjective and imaginative ability. One person may "conceive a possible experiment" while another may not. Thus our definition of which experiments are "conceivable" or not depends entirely on our imagination. It does not depend on objective facts at all. For example:

I can conceive of an experiment to test for creation vs. evolution. I can build a time machine, travel 6,000 years in the past, and see if there is a Garden east of Eden with two naked people in it (as predicted by creationism), or countless tribes of nomadic men and women settling into agriculture. This would certainly falsify creationism or evolutionism once and for all. But the experiment cannot be conducted, because I don't have a time machine. Consequently, although this experiment is conceivable, the ideas are still not falsifiable, because the experiment cannot be conducted.

Clearly, defining ideas as falsifiable when they could "conceivably" be falsified is not a useful definition, for two reasons:
 * First, scientists conceive of new experiments that were once inconceivable on a daily basis, thus making unfalsifiable ideas falsifiable. Unfalsifiable ideas are in fact the lifeblood of science, because they are the fuel that drives the experiments of tomorrow.
 * Second, the definition is not useful because it leaves the criteria for "science vs. non-science" entirely in the imagination of the scientist. For while many experiments may be conceived, they are not useful unless they can be conducted.

Falsifiability as requiring a possible experiment
This leaves us with the second definition: "Ideas are falsifiable when they are capable of being tested under today's scientific knowledge." This leaves us with a much better defined list of ideas which are falsifiable and those which are unfalsifiable. Falsifiable ideas can be tested today, and unfalsifiable ideas cannot be tested today. There is no ambiguity. Nothing is left to our imagination. The experiment either can be conducted or cannot be conducted.

This leads us to a second point: Unfalsifiable ideas are not necessarily false. We simply can't test them. If we adopt the first definition of falsifiability, that we must be able to "conceive" of an experiment to test the idea, then unfalsifiable ideas are useless, because they can never be tested and thus never become science.

But if we adopt the second definition of falsifiability, that we must be able to perform the experiment to test the idea, then we acknowledge that things which are not testable today may become testable tomorrow, and the goal of science becomes to expand the range of human knowledge by finding ways to test what is not yet testable. Under this definition, unfalsifiable ideas become the lifeblood of science, because it is from them that new experiments are tested, new discoveries made, and new science developed.

Conclusion
So in review, when we define as falsifiable ideas which may "conceivably be tested," we call things unfalsifiable and unscientific when we cannot "conceive" of an experiment to test them, and call things falsifiable and scientific when we can conceive of such an experiment. But no actual experiments need be conducted. Therefore there is no objective test to determine whether or not an idea is scientific. The whole process takes place in our imagination, and is subject to the scope of our imagination. And if a person is incapable of imagining a test for an idea, then that idea becomes eternally unfalsifiable and unscientific, never to be tested. Ideas which may be true are tagged as unscientific simply because scientists cannot yet test them.

In the end, a superficial definition of falsifiability is used to exclude those ideas which, although possibly true, do not fit into the scientist's "paradigm."

But when we define as falsifiable those ideas which may "be tested today," we call things unfalsifiable when we cannot test them and falsifiable when we can test them. Consequently, there is an objective test to determine which are falsifiable and which are not; it does not depend on our imagination, it depends on objective science. Further, unfalsifiable ideas are not seen as a roadblock to science, but as the future of science, as scientists develop and improve their ability to experiment, and turn unfalsifiable ideas into falsifiable ones.