标题: 请教一下充分必要条件的判断 [打印本页] 作者: 王Alcal1011 时间: 2010-6-11 14:27 标题: 请教一下充分必要条件的判断 9. A scientific theory is a good theory if it satisfies two requirements, It must accurately describe a large class of observations in terms of a model that is simple enough to contain only a few elements, and it must make definite predictions about the results of future observations, For example, Aristotle’s cosmological theory, which claimed that everything was made out of four elements---earth, air, fire, and water---satisfied the first requirement, but it did not make any definite, Thus, Aristotle’s cosmological theory was not a good theory. If all the statements in the passage are true, each of the following must also be true EXCEPT: (A) Prediction about the results of future observations must be made by any good scientific theory. (B) Observation of physical phenomena was not a major concern in Aristotle’s cosmological Theory (C) Four elements can be the basis of a scientific model that is simple enough to meet the Simplicity criterion of a good theory. (D) A scientific model that contains many elements is not a good theory (E) Aristotle’s cosmological theory described a large class of observations in terms of only four elements.
答案是B
想问的是我最开始觉得A也应该选，主要是不知道怎么区分充分必要条件。 “A scientific theory is a good theory if it satisfies two requirements”，这句话感觉是只要满足这两个条件，就是好理论，=〉充分条件 "it must"感觉又是个必要条件 请问大虾们怎么判断 作者: fjatpku 时间: 2010-6-11 22:30
所以这个其实是充要条件作者: 小火凤儿 时间: 2010-7-23 05:07
if后面连接着的是充分条件，it must的存在是不能改变充分条件这个性质的。
这个题目本来是有逻辑错误的，因为即使充分条件中的一个不能实现，也无法确定必要条件不成立，即无法判断“Aristotle’s cosmological theory was not a good theory.” 我觉得这就是问题tricky的地方，所以它是在问，如果这样的论述没有问题，需要什么条件成立，或者什么条件不会导致这种论述有矛盾之处。
A的意思可以这么理解，any good scientific theory can prediction about the results of future observations，这个就是补充了一个必要条件，这样可以使上面的论述不存在逻辑漏洞。 D也是补充了一个必要条件。
C和E只是paraphrase／strengthen the argument that ristotle’s cosmological theory, which claimed that everything was made out of four elements---earth, air, fire, and water---satisfied the first requirement。