It may seem obvious that this question should be answered in the negative, and so it unquestionably should be. But there always has been much cloudiness as to what constitutes invention in our own minds; and it must be admitted that the dividing line is not immediately obvious between invention and the art of meeting difficulties with resourcefulness, or between invention and the act of solving any of the perplexing riddles of our daily lives. It may be declared with confidence, however, that the difference between invention and any one of these other acts is that, while invention ends in performing such acts, it begins with an exercise of the imagination. A man who designs an engine to fulfil a stated purpose, who solves any problem whatever that is presented to him from outside, simply accomplishes a task that is given to him to accomplish; whereas, while the inventor accomplishes a similar task, he does it as a second step in a task that was not given him to accomplish, but that he himself had pictured to himself. The act of inventing consists of three separate acts--the act of conceiving, the act of developing, and the act of producing. Of these three acts, that of conceiving is obviously not only the first, but also the most important, distinctive and unusual. For every real invention, there have been countless constructive acts. In the invention of the bow and arrow, the conception was probably instantaneous and unbidden. The subsequent work of developing the conception into material and practical shape was probably one of long duration, consisting of many acts, accompanied with many difficulties and disappointments, and accomplished finally in the face of much active and passive opposition. * * * * * The Old Stone Age gradually developed into the New Stone Age at different times in different localities, as successive improvements in implements were made. The New Stone Age was distinguished from its predecessor mainly by the fact that the principal weapons and utensils were formed into regular shapes, polished into smoothness, and in many cases ground to sharp points and keen cutting edges. These improvements made the implements more effective both as weapons and as utensils, by facilitating not only cutting but penetration. How much invention was needed to make these improvements, it is not easy to decide; but probably only a little was required, and that of an order not very original or high; for the improvements were rather in detail than principle. Perhaps their character can be best indicated by saying that they were improvements, rather than inventions of a basic kind.