反証法重要嗎? 直接証法与反証法好比是通向同一目的地的两条道路。前者径直,后者曲折。如若直路好走,我們当然选择直路;但是,如果直路布滿荊棘,崎呕难行,那我們就宁愿走那条虽曲折但較好走的路了。至于直路閉塞断絕,那就非走弯路不可了。在証明时所发生的可能情况与此甚为类似。有时虽能用直接証法,但反証法来得简便,我們宁愿用反証法;亦有时根本就不能 Is counter-evidence important? Direct and counter-evidence are like two paths to the same destination. The former is straight and the latter is winding. If the straightway is good, we will certainly choose the straight road. However, if the straight road is full of thorns and it is difficult to carry out, then we would rather take the winding road but it is better to go. As for the blocking of the straight road, it would be a detour. The possible situations that occur at the time of certification are similar to this. Although direct evidence can sometimes be used, counter-evidence is easier to use. We prefer to use counter-evidence; sometimes we cannot use it at all.