Let us recur to our instance of a blur in motion appearing at a distance. We wonder what _the thing is_, _i.e._ what the _blur means_. A man waving his arms, a friend beckoning to us, are suggested as possibilities. To accept at once either alternative is to arrest judgment. But if we treat what is suggested as only a suggestion, a supposition, a possibility, it becomes an idea, having the following traits: (_a_) As merely a suggestion, it is a conjecture, a guess, which in cases of greater dignity we call a hypothesis or a theory. That is to say, it is _a possible but as yet doubtful mode of interpretation_. (_b_) Even though doubtful, it has an office to perform; namely, that of directing inquiry and examination. If this blur means a friend beckoning, then careful observation should show certain other traits. If it is a man driving unruly cattle, certain other traits should be found. Let us look and see if these traits are found. Taken merely as a doubt, an idea would paralyze inquiry. Taken merely as a certainty, it would arrest inquiry. Taken as a doubtful possibility, it affords a standpoint, a platform, a method of inquiry. [Sidenote: Pseudo-ideas] Ideas are not then genuine ideas unless they are tools in a reflective examination which tends to solve a problem. Suppose it is a question of having the pupil grasp _the idea_ of the sphericity of the earth. This is different from teaching him its sphericity _as a fact_. He may be shown (or reminded of) a ball or a globe, and be told that the earth is round like those things; he may then be made to repeat that statement day after day till the shape of the earth and the shape of the ball are welded together in his mind. But he has not thereby acquired any idea of the earth's sphericity; at most, he has had a certain image of a sphere and has finally managed to image the earth after the analogy of his ball image. To grasp sphericity as an idea, the pupil must first have realized certain perplexities or confusing features in observed facts and have had the idea of spherical shape suggested to him as a possible way of accounting for the phenomena in question. Only by use as a method of interpreting data so as to give them fuller meaning does sphericity become a genuine idea. There may be a vivid image and no idea; or there may be a fleeting, obscure image and yet an idea, if that image performs the function of instigating and directing the observation and relation of facts. [Sidenote: Ideas furnish the only alternative to "hit or miss" methods]