The Standards Of Evaluating Argument In Informal Logic

As a branch of logic, informal logic appeared in Europe and America during the 1960s-1970s, meeting the claim that logic should pay close attention to daily life. Nowadays it has been a movement in the international academic world with its top task of evaluating ordinary argument reasonably.During the course of argument studying, it is found that validity (exactly, deductive validity) is the standard of evaluating argument in formal logic. However, the standard finds itself in a difficult position when it is used for ordinary argument. First, all the forms of those arguments which accord with the standard of deductive validity are not always reasonable; Second, all the forms of ordinary arguments which are reasonable are not always in accordance with the standard of deductive validity. Thus it is necessary to revise the concept of validity so that it can be used for the evaluation of ordinary argument. And the concept is revised by informal logic in two ways: One way is to get rid of some forms with deductive validity in formal logic, which restrict the intention of the concept of deductive validity; Another way is to extend the possible situations of the extension of the concept of validity, so that validity means that argument is reasonable from certain aspect.Based on the revised concept of validity, foreign scholars raise some new standards for evaluating argument: deductive validity, inductive validity, substantial validity, informal validity, pragmatic validity, relevant validity, rhetoric validity, conventional validity. Though the above standards are all reasonable, they are in disorder and should berearranged. These standards can be divided into four groups: logical, including deductive validity and inductive validity; substantial, including substantial validity, informal validity and substantial relevant validity; rhetoric, rhetoric validity; pragmatic, including pragmatic validity, conventional validity and pragmatic relevant validity.Otherwise in some case all the standards are not so enough to evaluate argument validly. Other theories should be investigated and then used for reference. Theory of presupposition on argument in traditional logic is one of such theories. The research about this theory has found that principle of reason is the real presupposition of argument, while principle of difference, principle of possibility and principle of question are not, as they are only the demands of argument. Garssen' s principle of cooperation is another theory that can be applied in evaluating argument. Criterion of manner from principle of cooperation can introduce manner validity and concise validity for evaluating argument. Thus ,all together there are five different kinds of standards applied to evaluate argument: logical, including deductive validity and inductive validity; substantial, including substantial validity, premise validity and substantial relevant validity; rhetoric, including rhetoric validity and concise validity; pragmatic, including pragmatic validity, conventional validity and pragmatic relevant validity; linguistic, manner validity. The above standards evaluate argument from five aspects, and they are decided by characters of ordinary argument. Compared with the criterions of argument in traditional logic, the above standards can evaluate argument more comprehensively ,more specifically and more accurately.The new standards of evaluating argument can be used to explain whywe evaluate ordinary argument as: true or false argument, reasonable or unreasonable argument, good or bad argument, which is the result of using different new standards.Our study on informal logic isn' t so deep yet today, but the subject that use what standards to evaluate ordinary argument is completely new and full of life.