The world and the things in it are directly accessible to our senses and our judgment. How long has the world been in existence and how did it come to be? The answers to these questions also we do not know through our senses, and we must prove them by a chain of reasoning. There are several possibilities. The world just as it is may have existed from eternity. If so nobody made it; it just existed, and we have no proof of God. The world in its present form might have proceeded from a primitive matter. This hypothesis only removes the problem further back. For, leaving aside the question how did this prime matter develop into the complex world of our experience, we direct our attention to the prime matter itself, and ask, Has it existed from eternity or did it come to be? If it existed from eternity, then nobody made it, and we have no proof of a God, for by God we mean an intelligent being acting with purpose and design, and the cause of the existence of everything in creation. The third alternative is that whether the world was developed out of a primitive matter or not, it at any rate, or the primitive matter, as the case may be, was made in time, that is, it was created out of nothing. If so there must have been someone who created it, as nothing can create itself. Here we have proof of the existence of God. It follows therefore that we must first show that the world is not eternal, that it came to be in time, and this is what Saadia does. Here are some of his proofs. The world is finite in magnitude. For the world consists of the earth, which is in the centre, and the heavens surrounding it on all sides. This shows that the earth is finite, for an infinite body cannot be surrounded. But the heavens are finite too, for they make a complete revolution in twenty-four hours. If they were infinite it would take an infinite time to complete a revolution. A finite body cannot have an infinite power. This Saadia regards as self-evident, though Aristotle, from whom this statement is derived, gives the proof. Hence the force or power within the world which keeps it going is finite and must one day be exhausted. But this shows also that it could not have gone on from eternity. Hence the world came to be in time.[52] Another proof is based on the composite character of all things in heaven and earth. Minerals, plants and animals are made up of parts and elements. The heavens consist of spheres, one within the other. The spheres are studded with stars. But composition implies a time when the composition took place. In other words, the parts must have been there first and somebody put them together. Hence the world as we see it now is not eternal.[53]