that the size of the lead is considerably exceeded by the size of the wood. Finally, the converse declaration must be made about things that are lighter: for one thing must be deemed lighter, if when a piece of it is taken, equal in size to a piece of the other, it is found to be less in heaviness; as, if we take two pieces, one of wood, the other of lead, which are equal in size, but the piece of wood exerts less weight than the piece of lead, then, rightly, it must be declared that wood is lighter than lead.

That it has been established by nature that heavy things are in a lower place, and light things in a high place, and why.

Since things that are moved naturally are moved towards their proper places, and since the things that are moved are either heavy or light, it must be understood which are the places of heavy things, and which are those of light ones, and why. Now, every day we observe with our senses, that the places of heavy things are those that come near the centre of the world, and the places of light things are those that are farther distant from it; consequently, that such determined places were prescribed for them by nature is not something that we may doubt; but it can be called into question, on the other hand, why prudent nature has observed such an arrangment in distributing places, and not the opposite one. Now, from what I have read, no other cause of this distribution is adduced by philosophers, except that all things had to be arranged in a certain order, and it pleased Supreme Providence to distribute them in this one; and it seems that Aristotle also adduces this cause in Physics, book VIII, text 32, [255b15-17], when, asking why heavy things and light ones are moved towards their proper places, he supposes that the cause is because they are by nature suited to be carried somewhere, that is, the light upward, and the heavy downward. {1} And yet, if we examine the matter more attentively, we certainly shall not be able to think that there was no necessity or utility in nature's making such a distribution, but that it acted only according to whim or some kind of chance. Since I considered carefully that it was quite impossible to think this of provident nature, I scrupulously tried from time to time to imagine some cause, which would be, if not necessary, at least appropriate and useful: and indeed, I have discovered that it is not without the highest justification and the greatest prudence that nature has chosen this distribution. Indeed, since, as it has pleased more ancient {1} philosophers to assert, there is but one matter of all bodies, and those bodies are heavier that contain a greater number of particles of this matter in a narrower space {2} - as these same philosophers, who were perhaps unjustly