On Practical Reasoning

Since Aristotle,the issue of practical reasoning has always been being discussed by philosophers.But there are still many controversies about what is practical reasoning and what are differences between practical reasoning and theorical reasoning.To solve these two questions,we need clarify the concept of practical reasoning and the criterion of distinguishing between practical reasoning and theorical reasoning.Generally speaking,reasoning is constituted by sentences in some way.Understanding of meanings of sentences is crucial to judge the validity of reasoning.Therefore,the judgement criterion of judging meanings of sentences should be figured out before studying any forms of reasoning.Logical Positivism holds that the judgement criterion of meanings of sentences is principle of verifiability,and Pragmatism beliefs that the meanings of sentences are judged by the practical differences which are brought about by sentences to speakers.Comparing these two judgement criterions we find that whether empirical test in principle of verifiability or the practical consequences which are emphasized in practical differences,both accept the role of experiences.The difference is that principle of verifiability is faced with some controversies,such as self-refutation and vagueness of subject of verification.Because of this,more and more philosophers doubt its validity.However,there are not problems in Principle of Practical Differences,so Principle of Practical Differences is superior to principle of verifiability,expect that it is still revised.I hold that Principle of Practical Differences is the criterion of judging meanings of propositions.We can use judgement criterion of meanings of sentences to classify types of sentences.According to their practical differences,sentences could be divided into theorical sentences and practical sentences.Theorical sentences express beliefs,while practical sentences express intentions.Reasoning is made of sentences and is a goal-directed thinking activity by subject,so we can classify reasonings by types of sentences.Theorical reasoning concerns to beliefs,while there are controversies about what practical reasoning concerns to.Since Aristotle,many philosophers claim that the conclusion of practical reasoning is an action or a belief relating to action.However,there are many objections to this idea,I claim that the conclusion of practical reasoning is a mental state,intention.Alike theorical reasoning,there is no logical necessity between conclusion and premise of practical reasoning,so modus ponens does not work here.Practical reasoning is similar to probability reasoning,it has a defeasible feature.The conclusion of practical reasoning concerns to an intention of someone should or must do something.But there is still a problem.How to distinguish the conclusion of a reasoning is an intention or a belief?I claim that attitudes can be used to distinguish types of reasonings,and if the attitude of a reasoning's conclusion is an intention,then this reasoning is a practical reasoning.The reasoning is theorical reasoning whose attitude of conclusion is a belief.in English grammar,intention is not obvious in a proposition,so it is not easy to distinguish reasoning by intention.In this case,I hold that we can use means of purpose implications to classify attitudes and types of reasonings.With mark of attitudes and purpose implications,I clarify the requirement and basic permission of practical reasoning and prove that practical reasoning is distinct with theorical reasoning.The conclusion of this paper is that,reasoning is a goal-directed mental process by a subject,which infers a new attitude from old attitudes.Reasoning could be divided into theorical reasoning and practical reasoning.Theorical reasoning is about beliefs,and practical reasoning is about intentions.Reason only has an assistant role in reasoning.Practical reasoning is distinct with theorical reasoning.