Analysis Of LLera’s Study Of Abduction

Abductive reasoning is the inferential behavior that seeks explanation for abnormal phenomenon, the reasoning under situation which doesn’t provide complete information. It always occurs when the new experience collides with old experience or there is a cognitive conflict, which calls for a reasonable explanation. It is C.S.Peirece who firstly put forward this reasoning form and classified it as a type of reasoning that is distinct from deduction and induction. Peirce not only established abduction as a kind of logic, but he also firstly gave the pattern of abduction, a form of syllogism.With the study of artificial intelligence, especially the logical programing, knowledge composition and expert Telemedicine System, proceeds rapidly, the study of abduction, which has been ignored for a long term, revives again. The present study on abduction focuses more on the programing and systemization of abductive form, and aims to imitate the process of human recognition more concisely and improve machine learning. A.A.LLera is an expert in the study of abduction in present day. Unlike using modal logic or mathematical probability, which is the common method in this field, she creates a new approach which applied the logic tree to study the reasoning procedure of abductive reasoning and programed it successfully. The value of her work is that she didn’t limit her perspective on whether θ┝Φ stands or not, but on whether the logic tree of θ∪{-φ} is closed or not. However, the branch of logic tree will begin a geometric growth if it is too complex.As for belief revision, LLera set forward that there are two revising mode when new information contradicts with the old information base. They are the global strategy and the local strategy. The difference between them is that the former directly deletes one party of the contradiction while the latter substitutes "T" for the branch of a formula. The two mode have their strength and weakness separately. The global strategy changes more content more completely and thus is more succinct and convenient; the local strategy changes less but is more redundant.After reflecting on Pierce and LLera’s idea on abduction, this thesis has following claims:abduction is a dynamic process because of the causal-effect chain and the stratification of reasons; the key point of abduction is to enlarge the background knowledge as more as possible, the enlargement of background knowledge and the value of abduction is a counter-balance, which is a compromise as regards the economy; abductive reasoning proceeds in a curved line with collecting more evidence, every stage lies at a higher level than the next stage; the final abduction is the final maximal enlargement for a closed system.