Saturday, December 31, 2011


Introduced by Charles Sanders Peirce, abduction is a way of logical reasoning. The form of reasoning is as follows:

  • There is a surprising fact C
  • If H is true, the existence of C is natural and reasonable
  • Thus hypothesis H exists

Relationship and difference among three logical reasonings

Including abduction, there are mainly three types of logical reasoning, i.e. deduction, induction and abduction. There relationship of three types of reasoning in scientific discoveries is as follows: one lead to a hypothesis through abduction, then one logically prove it using deduction, and finally they prove the applicability of facts through empirical research (induction).

Following mathematical logical rule, deduction is strict and strong reasoning. Using deduction, one can come to the conclusion from premise almost straightforwardly. There is little chance of making fallacy when one is trained to make deductive reasoning. However, using deduction only, one cannot get to the leaping conclusion such as scientific discovery and innovation.

Induction and abduction can lead to the leaping conclusion, but the big difference between them is that whereas inductive reasoning just leads to general conclusion by summing up individual facts, abductive reasoning introduces hypothesis, which is critical in scientific theory or innovation. Bertrand Russell emphasized the importance of hypothesis in criticizing excessive emphasis on induction. He said:

“Bacon's inductive method is faulty through insufficient emphasis on hypothesis. He hoped that mere orderly arrangement of data would make the right hypothesis obvious, but this is seldom the case. As a rule, the framing of hypotheses is the most difficult part of scientific work, and the part where great ability is indispensable. So far, no method has been found which would make it possible to invent hypotheses by rule. Usually some hypothesis is a necessary preliminary to the collection of facts, since the selection of facts demands some way of determining relevance. Without something of this kind, the mere multiplicity of facts is baffling.”

Bertrand Russell, A history of western philosophy (4th printing), pp544 – 545

Conditions of abductive hypothesis

Peirce said there are four conditions in abuductive hypothesis.

  • The hypothesis is the most likely one among others
  • The hypothesis is simple, and using the hypothesis the facts are more simply described
  • The hypothesis can be tested
  • The cost of testing the hypothesis is lower than testing others

Rule of thumbs of abduction

Although the organized rule of introducing hypothesis is not in place even now, curiosity, creativity and imagination must be there. Innovators and scientists come up with new ideas from usual lives, as they don’t lose curiosity in things and find surprising facts in ordinary set-up. So, in a sense, the training to be innovative is not to lose child-like wonder. Creativity and imagination often come from the knowledge and experience in different fields.

Deductive method under the name of “logical thinking” has gained popularity in business society. Granted, deductive reasoning is prerequisite in everything, but we need to know the limitation. As computers would soon replace the role of deductive reasoning, Deduction alone is not enough to survive in 21st century. Now is the time to learn abductive reasoning.

Reference: アブダクション」(Japanese)、 米盛裕二、勁草書房

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