![]() ![]() They evidently forget that neither deduction nor induction can ever add the smallest item to the data of perception and, as we have already noticed, mere percepts do not constitute any knowledge applicable to any practical or theoretical use. ![]() Many logicians, however, leave it unclassed, a sort of logical supernumerary, as if its importance were too small to entitle it to any regular place. But all the objects of logical study have to be classifled and it is found that there is no other good class in which to put abduction but that of inferences. It is equally easy to define inference so as to exclude or include abduction. The mode of suggestion by which in induction the hypothesis suggests the facts is by contiguity, – familiar knowledge that the conditions of the hypothesis can be realized in certain experimental ways.Īny novice in logic may well be surprised at my calling a guess an inference. The mode of suggestion by which, in abduction, the facts suggest the hypothesis is by resemblance, – the resemblance of the facts to the consequences of the hypothesis. In induction the study of the hypothesis suggests the experiments which bring to light the very facts to which the hypothesis had pointed. In abduction the consideration of the facts suggests the hypothesis. Induction makes its start from a hypothesis which seems to recommend itself, without at the outset having any particular facts in view, though it feels the need of facts to support the theory. ![]() Abduction makes its start from the facts, without, at the outset, having any particular theory in view, though it is motived by the feeling that a theory is needed to explain the surprising facts. The method of either is the very reverse of the other’s. But for all that, they are the opposite poles of reason, the one the most ineffective, the other the most effective of arguments. Abduction and induction have, to be sure, this common feature, that both lead to the acceptance of a hypothesis because observed facts are such as would necessarily or probably result as consequences of that hypothesis. Nothing has so much contributed to present chaotic or erroneous ideas of the logic of science as failure to distinguish the essentially different characters of different elements of scientific reasoning and one of the worst of these confusions, as well as one of the commonest, consists in regarding abduction and induction taken together (often mixed also with deduction) as a simple argument. It is the first step of scientific reasoning, as induction is the concluding step. Ultimately, the circumstance that a hypothesis, although it may lead us to expect some facts to be as they are, may in the future lead us to erroneous expectations about other facts, – this circumstance, which anybody must have admitted as soon as it was brought home to him, was brought home to scientific men so forcibly, first in astronomy, and then in other sciences, that it became axiomatical that a hypothesis adopted by abduction could only be adopted on probation, and must be tested.Ībduction, on the other hand, is merely preparatory. What are to be the logical rules to which we are to conform in taking this step? There would be no logic in imposing rules, and saying that they ought to be followed, until it is made out that the purpose of hypothesis requires them. I reckon it as a form of inference, however problematical the hypothesis may be held. This step of adopting a hypothesis as being suggested by the facts, is what I call abduction. A hypothesis then, has to be adopted, which is likely in itself, and renders the facts likely. Accepting the conclusion that an explanation is needed when facts contrary to what we should expect emerge, it follows that the explanation must be such a proposition as would lead to the prediction of the observed facts, either as necessary consequences or at least as very probable under the circumstances.
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