Another way to find whether an analogy is fallacious is to see whether you can discover a counter analogy. Surely this is the most effective practice in refuting analogy in argument. This suggests the case of the man who had a ticket from New York to Chicago, and tried to use it from Chicago to New York. The railroad refused to accept it, whereupon the man brought suit. The lawyer for the defendant, in the heat of the debate, said, “Why, a man might just as well pay for a barrel of potatoes and then demand a barrel of apples!” Whereupon the attorney for the plaintiff replied, “It would be rather like a grocer selling a man a barrel of potatoes and then trying to compel him to eat them from the top down, refusing to allow him to turn the barrel upside down and begin eating them from the bottom up.” It is best to avoid analogy except for purposes of suggestion, or as a rhetorical device for explaining an idea already arrived at by other means. I have been forced to defend my advice to take as many viewpoints as possible, by pointing out that the conclusions obtained from these viewpoints might disagree; in fact would be almost sure to disagree. Of course, this disagreement might be avoided if we allowed the conclusions reached by one method or viewpoint to influence our conclusions in another. But if we do this we give our problem more shallow treatment, and we are not so sure of a result when we get it. When a mathematician adds a column of figures from the top down, he confirms by re-adding from the bottom up. He knows that if he added in the same manner the second time he would be liable to fall into the same errors. And in thinking, when we leave one method and take up another, we should try to forget entirely the first conclusion and begin on the problem as if we had never taken it up before. After we have taken up all the applicable methods, then, and then only, should we begin to compare conclusions.