假言三段论的假设
l 具有“如果p,则q的形式，与之相矛盾的形式：“P且非Q”或“非Q且P”
l 当一些推论由问题的时候，一定要用一些非常强的假设，如only ,the only ,wheather---or not ,all
1 If the airspace around centrally located airsports were restricted to commercial airliners and only those private planes equipped with radar ,most of the private planes traffic would be forced to use outlying airfields .such a reduction in the amount of private-plane traffic would reduce the risk of midair collision around the centrally located airports.
标准形式：前提

1If the airspace around centrally located airports were restricted to commercial airliners and only those private planes equipped with radar.
结论：most of the private planes traffic would be forced to use outlying airfields.

2 In order to be happy , one must have an intimate relationship with another person .yet the world’s greatest composers spent most of their time in solitude and had no intimate relationships.so the psychological theory must be wrong.
标准形式：if p( to be happy),then q (one must have an intimate relationship with another person ).
结论：But its wrong.┐q
前提：p
3 if the edition sold in Britain were in American English, its idioms and spellings would appear to British readers to be strikingly American
结论： to conflict with the novel’s setting.
标准形式：思路归缪法（排除其他可能）注意 NO
前提：
4 In a bureaucracy ,all decisions are arrived at by a process that involves many people. There is no one person who has the authority to decide whether a project will proceed or not .
结论： in bureaucracy ,risky projects are never undertaken.
标准形式：
1) only one person decision is a risky project.
2) 排除
5 the apple sold in this cafeteria are greasy. The cashier told me that the apples are in that condition when they are delivered to the cafeteria and that the cafeteria does not wash the apples it sells. Most fruit is sprayed with dangerous pesticides before it is harvested,and is dangerous until it is washed .Clearly, the cafeteria is selling pesticide-covered fruit,thereby endangering its patrons.
标准形式：1）彻底排除在进入饭店以前被清洗的可能
二，小结：如果论证都是有明显缺陷的，假设的作用在于弥补其中的缺陷。而对于一个一个论证而言，最严重的缺陷就是反例的存在，即与论证的结论相矛盾的命题的存在。从这个角度而言，假设的作用就是防止反例的产生，排除反例的存在。然而，要弥补一个有缺陷的论证，排除一个有缺陷的论证的反例，其假设一定视角绝对的，或者说是较苛刻的。这种假设在语言的标志是使用诸如ALL,EVERY,NO,ONLY ,AT LEASTZ这样的词