The belief that any legal thinking and reasoning can be reconstructed into a deductive argument is called 'deductivism'. According to deductivism, there lies a hidden assumption in the rule-following or rule-application that works in the legal reasoning; if this assumption is restored to a clear universal premise, then the whole argument is to be translated into a deductive argument. However, deductivism does not prove to be the most explanatory model of facts of legal reasoning. In the first place a lawyer, or generally, one who legally reasons, can not avoid performing a series of interpretation of the given rule(interpretation of the meaning of the rule, that of the fact and that of the reason for the rule), before he follows or applies it. Furthermore, as Dworkin tries to show, the reasoning that will arrive at the decision about a given issue that should be made by the law court on the basis of the meaning or contents of the law is not separated from the reasoning that will establish the meaning or contents of the law about that issue. In brief, reasoning operative in decision is not separated from reasoning establishing the meaning. By the way, reasoning establishing the meaning is an interpretation, i.e. a process of giving a meaning. Thus, giving a meaning as interpretation is not detached from the deductive reasoning. In addition to this point, a historical consideration of the concept of 'argument' supplies another ground for the criticism of deductivism. The idea of Aristotle's rhetorical argument and the ancient conception of topoi show that the driving force and thrust to start and build legal reasoning as a practical rationality comes not from deductivism, but from dialectical spirit, which orients itself at a 'good' argument. And the dialectical training should be aimed at by education of philosophy as propaedeutics for legal education.