Another common type of reasoning is the search for causes and results.另一个普遍的推理类型是因果的研究。
We want to know whether cigarettes really do cause lung cancer. 我们希望知道香烟是否确实引起肺癌,
and what causes malnutrition,the decay of cities,or the decay of teeth.以及是什么引起了营养不良,城市的衰退或牙齿的腐朽.
We are equally interested in effects:我们对同样的结果感兴趣：
what the effect of sulphur or lead in th atmosphere,of oil spills and raw sewage in rivers and the sea, 硫磺或铅在大气中有什么结果，原油泄漏和未处理的污水在江河、海洋中的影响,of staying up late on the night before and examination?考试前熬夜有什么影响？
Causal reasoning may go from cause to effect or from effect to cause.原因的推理可以从原因到结果或结果到原因.
Either way,we reason from what we know of what we want to find out,任何一种方法中，我们都是从已知到我们需要了解的东西
Sometimes we reason from an effect to a cause and then on to another effect.有时我们从一个结论推理出一个原因
Thus,If we reson that because the lights have gone out,the refrigerator won't work,因此如果我们推论因为光灭了，冰箱不工作.
we first relate the effect(lights out) to the cause(power off) and then relate that cause to another effect (refrigerator not working)我们首先把结果（灯灭了）和原因（停电）关联，然后又将那个原因与另一个结果（冰箱不会工作）相互关联.
This kind of reasoning is called,for short,effect to effect.这种推理方式简称为“结果到结果”。
It is quite common to reason through an extensive chain of causal relations.通过扩大的因果关系链推论是相当普遍的
When the lights go out we might reason in the following causal chain:当光熄灭我们可以按下列因果关系链推论：
Lighsout-prower off-refrigerator not working-temperature-will rise-milk will sour。灯灭-停电-冰箱不工作-温度上升-牛奶变酸.
In other words,we diagnose a succession of effects from the power failure,each becoming the cause of the next。换句话说，我们推论出由停电而产生的一连串的结果，每个结果成为下一个的原因
Prohibition
DO we need laws that prevent us from running risks with our lives?我们需要阻止我们以自己的生命冒险的法律嘛？
If so,the perhaps laws are needed prohibition the sale of cigarettes and alcoholic drinks.如果需要，那么也许需要法律来禁止出售香烟和酒精饮料.
Both products have been known to kill perple.人们知道两种产品都能致命.
The hazards of drinking too much alcohol are as bad as or worse than the hazards of smoking too many cigarettes.喝太多酒和抽太多烟同样地具有危害性或者更胜之。