to make good livestock fodder; then it was learned that potatoes could nourish people; and, later, potatoes began to be used for making vodka.
In regard to inventions, gradualness may be illustrated by the evolution of the stool. First people found that it was better to sit on a stump or a rock than on the ground. Then, noticing that a rock or a stump was too heavy to lug around, they built a stool consisting of a board and several legs. Next, to the stool they added a backrest, thus making a chair; to the chair, they added armrests, making an armchair. Then they began painting and padding the armchairs and chairs, and so on.
2. The law of dependence. An invention or discovery is conditioned on the prior existence of certain known discoveries and inventions. America would not have been discovered had ships and compasses not been known; the locomotive would not have been built had iron, water, and coal not been known, had wheels, rods, and boilers not been known, and so on. If potatoes grew only in America, they could not have been discovered before America had been; if the black swan lives only in Australia, the black swan could not have been seen before Australia had been. If the rings of Saturn can be seen through telescopes, then the telescope had to have been invented before the rings could have been seen. Thus we see that any invention or discovery depends on certain discoveries and inventions that had to have existed and been known earlier.
3. The law of combination. Any new discovery or invention is a combination of earlier discoveries and inventions, or rests on them. When I study a new mineral, I inspect it, I smell it, I taste it, that is, I combine the mineral with my senses. Then I weigh it and heat it, which is to say, I combine
