RAZD writes:
No matter how well established a theory is, it can never be more than possibly true, because inductive logic does not give you a conclusion of true\fact. This holds even when a theory is called a law. I believe that this is, in essence, your argument (or a major portion thereof) in this thread, yes?
Yes, that's essentially my position, although I would prefer to say that a theory is never more than
probably true. Much of the discussion in this thread has been driven by the assertion advanced by nwr that induction is
never used in science. I appreciate that you are bringing to this discussion a more nuanced examination of how both induction and deduction may be used in science.
In this regard, the inductive element in science is not to determine what is fact\true, but to show what should be tested to see if it can help define what is fact\true.
I think the words fact and true should be used with great care in science. Scientific knowledge is perpetually tentative. Scientists sometimes use deductive reasoning. And of course deductive conclusions are necessarily true when the premises are true. But I believe that the premises are often, if not always, subject to error and revision.
The important thing, as I see it, is that this process sifts evidence and concepts and eliminates falsified concepts while organizing facts into an explanatory framework -- our "best guess" or "best known explanation" of the evidence -- and that the pool of known evidence\facts is increased whether a theory is falsified or not. In this way the process is an incremental approximation of truth that continually gets closer to reality, even if it can't arrive at a definitive conclusion.
I agree with you, because I’m a scientific realist. An instrumentalist, however, would claim that there is no way to know whether we are getting closer to reality.
As we see above, the facts\truths that we can know are determined deductively from the original evidence and the added information from the testing. This knowledge is discovered by the testing and deductive evaluation parts of the process, not by the inductive process. Let's try an analogy:
I have a rifle set up on a fixed mount 1000 yards from a target. With the gun-sight I make my first approximation of aiming the rifle at the target. I take 10 shots with that setting, then measure the results. The scatter in the shots from their mean value determines how effectively the rifle reproduces the same results from a test, the difference between the mean value and the target center determines the accuracy of the initial approximation. I make a vertical adjustment in the rifle setup in the direction that the mean value was vertically off from the target center and repeat the shots and measurements, then make another vertical adjustment towards the center in proportion to the remaining delta to the center and the difference in the two shot patterns. I do the same thing in the horizontal adjustments. All else being equal, and not having any other variables that are not controlled by the rifle setting (variable cross-wind etc), I should be able in fairly short order to reach a reasonable accuracy within the ability of the rifle to reproduce the same results in repeated tests, regardless of where my initial shots ended up.
It is the deductive process in the evaluation of the evidence that brings the pattern closer to the target center. If I just relied on induction then I could go back and forth with varying degrees of success, but never approaching the center in the way that deductive analysis does. . . .
. . . Yet it is the deductive evaluation of the evidence that either invalidates the theory or shows that we have additional evidence that is consistent with the evidence used to formulate the theory. The deductive analysis of the results of testing brings us closer to reality, and this refines the inductive hypothesis for the next round of testing.
If I understand your position, you are saying we can make a prediction from a tentative theory and then measure how an actual experimental result differs is from the prediction. We can then modify the theory, make a new prediction, and see if we have gotten any closer to reality.
A problem I see with that approach is that, by adding
post hoc theory modifications, even a theory that is a poor representation of reality may become more accurate for the purpose of making predictions. By adding epicycles, for example, the Ptolemaic model became better at making predictions, but it never got any closer to reality.
Using cladistics to compare all the common and different elements you should then find that the most parsimonious explanation was that the dog-like fox was a descendant of wild foxes. {phase three}
This would be a statistically deduced most likely answer:
Linkquote:
Cladistics is also distinguished by its emphasis on parsimony and hypothesis testing (particularly falsificationism), rather than subjective decisions that some other taxonomic systems rely upon.[3]
This is the kind of rigorous empirical testing and deductive evaluation used in biology to validate common descent in the larger picture.
I can see how deduction plays a role. For example:
- Mammals have hair, produce milk, etc.
- New animal has hair, produces milk, etc.
- Therefore, new animal is a mammal.
But in the dog-like fox hypothetical, I think your conclusion is an inference to the best explanation rather than a deduction. In fact, you refer to it as the most likely answer. While descent from the current wild fox population is the most likely explanation, based on the evidence, you would not be able to rule out completely other possibilities. For example, the foxes may have descended from a dog-like fox ancestor that is now nearly extinct. I agree the latter explanation would be highly unlikely, but given the available evidence, it is not a logical impossibility.
Doesn’t your use of the term parsimonious suggest the use of non-deductive reasoning?
I agree that cladistics is less subjective than some other taxonomic systems, but I don’t think it is any more deductive.
If we were to start by assuming special creation of the dog-like fox, then we would test for elements that are not consistent with dogs, foxes, canines or mammals. Not finding any we would conclude that there is no evidence of any process other than common descent from existing species. This leaves special creation as god-directed evolution causing what we see as natural processes, and that still results in the most parsimonious explanation being that the dog-like fox was a (directed) descendant of wild foxes. As such your complaint is irrelevant.
Nicely done! I can see you have used deductive reasoning to show that, if the evidence supports common descent, whether that process is "natural" or God-directed is irrelevant. Nevertheless, the premise that the evidence supports common descent was derived non-deductively. You have again invoked parsimony in defense of the premise.
Edited by Stephen Push, : No reason given.
™ Version 4.2