11. REFLECTIVE THOUGHT.—If we ask our neighbor to meet us somewhere at a given hour, he has no difficulty in understanding what we have requested him to do. If he wishes to do so, he can be on the spot at the proper moment. He may never have asked himself in his whole life what he means by space and by time. He may be quite ignorant that thoughtful men have disputed concerning the nature of these for centuries past.
And a man may go through the world avoiding disaster year after year by distinguishing with some success between what is real and what is not real, and yet he may be quite unable to tell us what, in general, it means for a thing to be real. Some things are real and some are not; as a rule he seems to be able to discover the difference; of his method of procedure he has never tried to give an account to himself.
That he has a mind he cannot doubt, and he has some idea of the difference between it and certain other minds; but even the most ardent champion of the plain man must admit that he has the most hazy of notions touching the nature of his mind. He seems to be more doubtful concerning the nature of the mind and its knowledge than he is concerning the nature of external things. Certainly he appears to be more willing to admit his ignorance in this realm.
And yet the man can hold his own in the world of real things. He can distinguish between this thing and that, this place and that, this time and that. He can think out a plan and carry it into execution; he can guess at the contents of other minds and allow this knowledge to find its place in his plan.
All of which proves that our knowledge is not necessarily useless because it is rather dim and vague. It is one thing to use a mental state; it is another to have a clear comprehension of just what it is and of what elements it may be made up. The plain man does much of his thinking as we all tie our shoes and button our buttons. It would be difficult for us to describe these operations, but we may perform them very easily nevertheless. When we say that we know how to tie our shoes, we only mean that we can tie them.
Now, enough has been said in the preceding sections to make clear that the vagueness which characterizes many notions which constantly recur in common thought is not wholly dispelled by the study of the several sciences. The man of science, like the plain man, may be able to use very well for certain purposes concepts which he is not able to analyze satisfactorily. For example, he speaks of space and time, cause and effect, substance and qualities, matter and mind, reality and unreality. He certainly is in a position to add to our knowledge of the things covered by these terms. But we should never overlook the fact that the new knowledge which he gives us is a knowledge of the same kind as that which we had before. He measures for us spaces and times; he does not tell us what space and time are. He points out the causes of a multitude of occurrences; he does not tell us what we mean whenever we use the word "cause." He informs us what we should accept as real and what we should repudiate as unreal; he does not try to show us what it is to be real and what it is to be unreal.
In other words, the man of science extends our knowledge and makes it more accurate; he does not analyze certain fundamental conceptions, which we all use, but of which we can usually give a very poor account.
On the other hand, it is the task of reflective thought, not in the first instance, to extend the limits of our knowledge of the world of matter and of minds, but rather to make us more clearly conscious of what that knowledge really is. Philosophical reflection takes up and tries to analyze complex thoughts that men use daily without caring to analyze them, indeed, without even realizing that they may be subjected to analysis.
It is to be expected that it should impress many of those who are introduced to it for the first time as rather a fantastic creation of problems that do not present themselves naturally to the healthy mind. There is no thoughtful man who does not reflect sometimes and about some things; but there are few who feel impelled to go over the whole edifice of their knowledge and examine it with a critical eye from its turrets to its foundations. In a sense, we may say that philosophical thought is not natural, for he who is examining the assumptions upon which all our ordinary thought about the world rests is no longer in the world of the plain man. He is treating things as men do not commonly treat them, and it is perhaps natural that it should appear to some that, in the solvent which he uses, the real world in which we all rejoice should seem to dissolve and disappear.
I have said that it is not the task of reflective thought, in the first instance, to extend the limits of our knowledge of the world of matter and of minds. This is true. But this does not mean that, as a result of a careful reflective analysis, some errors which may creep into the thought both of the plain man and of the scientist may not be exploded; nor does it mean that some new extensions of our knowledge may not be suggested.
In the chapters to follow I shall take up and examine some of the problems of reflective thought. And I shall consider first those problems that present themselves to those who try to subject to a careful scrutiny our knowledge of the external world. It is well to begin with this, for, even in our common experience, it seems to be revealed that the knowledge of material things is a something less vague and indefinite than the knowledge of minds.
II. PROBLEMS TOUCHING THE EXTERNAL WORLD
CHAPTER III
IS THERE AN EXTERNAL WORLD?
12. HOW THE PLAIN MAN THINKS HE KNOWS THE WORLD.—As schoolboys we enjoyed Cicero's joke at the expense of the "minute philosophers." They denied the immortality of the soul; he affirmed it; and he congratulated himself upon the fact that, if they were right, they would not survive to discover it and to triumph over him.
At the close of the seventeenth century the philosopher John Locke was guilty of a joke of somewhat the same kind. "I think," said he, "nobody can, in earnest, be so skeptical as to be uncertain of the existence of those things which he sees and feels. At least, he that can doubt so far (whatever he may have with his own thoughts) will never have any controversy with me; since he can never be sure I say anything contrary to his own opinion."
Now, in this chapter and in certain chapters to follow, I am going to take up and turn over, so that we may get a good look at them, some of the problems that have presented themselves to those who have reflected upon the world and the mind as they seem given in our experience. I shall begin by asking whether it is not possible to doubt that there is an external world at all.
The question cannot best be answered by a jest. It may, of course, be absurd to maintain that there is no external world; but surely he, too, is in an absurd position who maintains dogmatically that there is one, and is yet quite unable to find any flaw in the reasonings of the man who seems to be able to show that this belief has no solid foundation. And we must not forget that the men who have thought it worth while to raise just such questions as this, during the last twenty centuries, have been among the most brilliant intellects of the race. We must not assume too hastily that they have occupied themselves with mere trivialities.
Since, therefore, so many thoughtful men have found it worth while to ask themselves seriously whether there is an external world, or, at least, how we can know that there is an external world, it is not unreasonable to expect that, by looking for it, we may find in our common experience or in science some difficulty sufficient to suggest the doubt which at first strikes the average man as preposterous. In what can such a doubt take its rise? Let us see.
I think it is scarcely too much to say that the plain man believes that he does not directly perceive an external world, and that he, at the same time, believes that he does directly perceive one. It is quite possible to believe contradictory things, when one's thought of them is somewhat vague, and