There Is No Positive Lightness in the Nature of Things

Abstract

Hitherto we considered the gravity, not of all fluid bodies, but only of water, quicksilver and others similar the ponderousness of which nobody questions. Obviously they strive downwards and descend. A problem arises concerning other bodies which seem to move upwards such as wood and others which rise in water. To attribute gravity to them appears to be against common sense. Nevertheless, with the best known philosophers, we shall attempt to show that all elementary fluid bodies are provided with gravity and that there is absolutely no positive lightness in nature. It must also be shown that all elementary bodies have the force to unite to form our system, i.e. they have the motive faculty of descending towards the centre of the terrestrial globe. This force is called gravity. Firstly, we shall examine the arguments of Aristotle expressed against Plato and Democritus who asserted the above mentioned opinions. Then we shall recall for examination the arguments of Aristotle himself by which he attempted to establish positive lightness. Thirdly, I will bring forwards demonstrations which show that there is no positive lightness. Finally, I will consider all which was indistinctly presented by the best peripatetics against the Platonic opinion and which led to my own idea.