The sys­tem­at­ic thinker is careful of the manner in which he marshals his difficulties. He knows that certain problems should properly be considered before certain others, and he saves himself labor and sometimes error by considering them in that order. Before asking himself how Government should cure a given social evil, he first asks whether it is the duty or even the right of the State to attend to that par­tic­u­lar evil at all. In other words, before asking what the State should do in any par­tic­u­lar case, he considers first what the proper sphere of government is. It must be admitted that a previous question often cannot be discovered until one has actually attempted the solution of a problem. In the foregoing instance, it would be difficult to determine the proper sphere of government by any other method than a con­si­der­a­tion of par­tic­u­lar cases where government interference suggests itself.

In fact, it is only by deep reflection on a subject that we come to realize most of the problems involved. You walk along the road with your friend the botanist and he stops to pick what looks to you to be a common wild flower. “Hm,” he muses, “I wonder how that got in this part of the country?” Now that is no problem to you, simply because you do not happen to know why that par­tic­u­lar flower should not be there—and what men do not know about they take for granted. Knowledge furnishes problems, and the discovery of problems itself constitutes an in­tel­lec­tual advance.

Whenever you are thrashing out a subject, write down every problem, difficulty and objection that occurs to you. When you get what you consider a satisfactory solution, see whether or not it answers all of them.

I have stated that method is essential to good thinking. I have given rules and examples of methodic thinking. But I do not want to create a false impression. If a man has not within him the materials of a thinker, no amount of method can make him one. Half the thinking process, as pointed out, depends on the occurrence of sug­ges­tions. The occurrence of sug­ges­tions depends on how ideas are associated in a man’s mind. While this depends to some extent on the education and the whole past life and environment of the individual, it depends far more on inborn mental qualities. All method can do is to awaken the most fruitful associations of ideas already in mind. Hence the more methods we adopt—the greater the number of views we take of any problem—the more solutions will suggest themselves.

There is one further reason why we should take as many different viewpoints as possible. In our example of the inheritance of acquired char­ac­ter­is­tics in animals, if we had been sure that the results of our deductive reasoning were correct, it would have been a sinful waste of time to experiment. But when we attack a problem by several methods we can compare the results from each. If these results agree we have good evidence that our solution is correct. But if we have adopted quite a number of viewpoints, and have not let the results of one influence those of the next, they are almost certain to be at variance. This means that we have erred in applying one or several methods. How are we to find which of the methods it was, and how are we to prevent such errors?

This is the subject of our next chapter.

III A FEW CAUTIONS

Thus far we have con­sidered only pos­i­tive and con­struc­tive think­ing, and means for ob­tain­ing relevant sug­ges­tions. We have had almost nothing to do with cautions, means for avoiding fallacy and error, and means for testing the truth and value of sug­ges­tions. Most writers who have discussed thinking have dwelt so much on the negative aspect—so much on what we should not do—and have so slighted the question of what we should do, that I have perhaps been led to adopt this order, more from a feeling of revolt than because it is logically better. But I believe I have logic on my side. Constructive methods make thinking “go”; cautions steer it in the right path. An auto­mo­bile with­out a steer­ing gear is almost as useless as one without a motor. But an auto­mo­bile can go without being steered, whereas it cannot be steered unless it is going.

But while with automobiles we can clearly divide moving from steering, we cannot do this with thinking. The two processes are so inextricably bound up, that we cannot engage in one without engaging in the other; we cannot even speak of one without implying the other. I have divided them for convenience of exposition. But in the last chapter we were forced to deal slightly with cautions, and here we shall have to consider constructive methods to some extent.

A case in point is clas­si­fi­ca­tion. In taking this up from a constructive standpoint, I remarked that all clas­si­fi­ca­tions ought to be logical. But I did not say what I meant by logical, nor did I tell how a logical clas­si­fi­ca­tion could be secured. The two most prominent errors made in classifying are (1) not making clas­si­fi­ca­tions mutually exclusive, (2) not making them cover all the objects or phenomena supposed to be classified.