Every mechanical invention arises from a need: from the strict necessity for individual preservation in the case of primitive man who wages war against the powers of nature; from the desire for well-being and the necessity for luxury in growing civilization; from the need of creating little engines, imitating instruments and machines, in the child. In a word, every particular invention, great or small, arises from a particular need; for, we repeat again, there is no creative instinct in general. A man distinguished for various inventions along practical lines, writes: "As far as my memory allows, I can state that in my case conception always results from a material or mental need.[124] It springs up suddenly. Thus, in 1887, a speech of Bismarck made me so angry that I immediately thought of arming my country with a repeating rifle. I had already made various applications to the ministry of war, when I learned that the Lebel system had just been adopted. My patriotism was fully satisfied, but I still have the design of the gun that I invented." This communication mentions two or three other inventions that arose under analogous circumstances, but have had a chance of being adopted.
Among the requisite qualities I mention the natural and necessary preëminence of certain groups of sensations or images (visual, tactile, motor) that may be decisive in determining the direction of the inventor.
(II) Mechanical invention grows by successive stratifications and additions, as in the sciences, but more completely. It is a fine verification of the "subsidiary law of growing complexity" previously discussed.[125] If we measure the distance traversed since the distant ages when man was naked and unarmed before nature to the present time of the reign of machinery, we are astonished at the amount of imagination produced and expended, often uselessly lavished, and we ask ourselves how such a work could have been misunderstood or so lightly appreciated. It does not pertain to our subject to make even a summary table of this long development. The reader can consult the special works which, unfortunately, are most often fragmentary and lack a general view. So we should feel grateful to a historian of the useful arts, L. Bourdeau, for having attempted to separate out the philosophy of the subject, and for having fastened it down in the following formulas:[126]
(a) The exploitation of the powers of nature is made according to their degree of power.
(b) The extension of working instruments has followed a logical evolution in the direction of growing complexity and perfection.
Man, according to the observations of M. Bourdeau, has applied his creative activity to natural forces and has set them to work according to a regular order, viz.:
(1) Human forces, the only ones available during the "state of nature" and the savage state. Before all else, man created weapons: the most circumscribed primitive races have invented engines for attack and defense—of wood, bone, stone, as they were able. Then the weapon became a tool by special adaptation:—the battle-club serves as a lever, the tomahawk as a hammer, the flint ax as a hatchet, etc. In this manner there is gradually formed an arsenal of instruments. "Inferior to most animals as regards certain work that would have to be done with the aid of our organic resources alone, we are superior to all as soon as we set our tools at work. If the rodents with their sharp teeth cut wood better than we can, we do it still better with the ax, the chisel, the saw. Some birds, with the help of a strong beak, by repeated blows, penetrate the trunk of a tree: but the auger, the gimlet, the wimble do the same work better and more quickly. The knife is superior to the carnivore's teeth for tearing meat; the hoe better than the mole's paw for digging earth, the trowel than the beaver's tail for beating and spreading mortar. The oar permits us to rival the fish's fin; the sail, the wing of the bird. The distaff and spindle allow our imitating the industry of insect spinners; etc. Man thus reproduces and sums up in his technical contrivances the scattered perfections of the animal world. He even succeeds in surpassing them, because, in the form of tools, he uses substances and combinations of effects that cannot figure as part of an organism."[127] It is scarcely likely that most of these inventions arose from a voluntary imitation of animals: but even supposing such an origin, there would still remain a fine place for personal creative work. Man has produced by conscious effort what life realizes by methods that escape us; so that the creative imagination in man is a succedaneum of the generative powers of nature.
(2) During the pastoral stage man brought animals under subjection and discipline. An animal is a machine, ready-made, that needs only to be trained to obedience; but this training has required and stimulated all sorts of inventions, from the harness with which to equip it, to the chariots, wagons, and roads with which and on which it moves.
(3) Later, the natural motors—air and water—have furnished new material for human ingenuity, e.g., in navigation; wind- and water-mills, used at first to grind grain, then for a multitude of uses—sawing, milling, lifting hammers; etc.
(4) Lastly, much later, come products of an already mature civilization, artificial motors, explosives,—powder and all its derivatives and substitutes—steam, which has made such great progress.