第二讲科学推理教材.ppt

Basic Types of Reasoning in Science 主讲人：万小龙、冉奎 本节内容 hypotheses：假说是科学推理中的一个基本概念。 deductive Reasoning：演绎推理 inductive Reasoning：归纳推理 statistical and Probabilistic Reasoning：概率推理 1 hypotheses everything is made of water. matter is continuous and infinitely divisible. the earth is fixed at the center of the universe. the earth moves around a stationary sun. light is made up of little particles. light is made up of waves. it will rain tomorrow. it rained last night. it is raining now. 1.1 what is a hypotheses Greeks: Hypotheses is the starting point of a debate. us：Hypotheses is a statement which we doubt its truth status.——relativity hypotheses are statements of assertions and judgments, their essential characteristic is that the are either true of false. empirical hypotheses: hypotheses whose truth of falsity would make a difference in what we should expect in our experience. hypotheses and fact scientific statement and metaphysical statement. 1.2 problems of hypotheses motivations: explain things; unify phenomena. problem of discovery problem of justification direct test: match the given hypothesis with reality the tower of Pisa is red. indirect test: comparing a logical consequence of the hypothesis with reality. the earth is round. logical consequence: the shadow of the earth is round. 严格来说，没有绝对的直接检验，这种区分是相对的。 1.3 logic of indirect test from hypothesis to implication H → I if H is true, then I is true. But I is found to be false. therefore, H is false. if H is true, then I is true. I is indeed found to be true. therefore there are some grounds for the truth of H. H: the figure is a square. I: it has 4 corners. 2 deductive reasoning the study of the notion of deduction and associated notions such as logical consequence, consistency, and contradiction belongs to the discipline know as deductive logic. deduction is a kind of argument. an argument has two components: the premises and the conclusion. P1, P2, P3, ...→ C read as P1, P2, P3, ...therefore C. 2.1 assess