And, since he lived in an island situated under the equinoctial line, all those circles cut the horizon at right angles and had alike reference to North and South, seeing both the poles appeared to him at once. He observed that when a star arose in a larger circle and another in a lesser, yet they both arose together and set at the same time, and he noticed it to be the case with all stars at all times. _Hayy concludes that the Heaven is of a spherical Figure._ Therefore, it was evident to him that the heaven was of a spherical figure. In this he was further confirmed by observing the return of the sun, moon, and the other stars to the East after their setting; and also because they always appeared to him of the same proportion of magnitude when they arose, when they were in the midst of heaven, and when they set; for if their motions had not been circular, they must have been nearer to sight at some time than at others; and then their dimensions would have appeared greater or lesser when they were nearer to him or further off. But since there was no such appearance, he felt assured that the figure of heaven was spherical. Then he considered the motion of the moon, and saw that it was carried from the East to the West as the other planets were. So that at length a great part of astronomy became known to him. It appeared to him, further, that the motions of the planets were in different spheres, all of which were comprehended in another that was above them all, and which turned about all the rest in the space of a day and a night. But it would be too tedious to set down, to explain in particular, how he advanced in this science; and what we have already said is quite sufficient for our present purpose. Now, when he had attained to this degree of astronomical science, he found that the whole of the heavens and whatever it contained was one thing composed of parts mutually joined together; and that all those bodies which he had before considered--as earth, water, air, plants, animals--were all of them contained in it, so that none of them went beyond its bounds. He found also that the whole body was like one animal in which the stars answered to the senses; the spheres joined together answered to the limbs; and all those bodies therein, which were liable to generation and corruption, resembled those things which are contained in the belly of an animal. _Hayy ponders over the Creation of the World._ Now, whereas it appeared to him that the whole world was only one Substance which stood in need of a voluntary Agent, and that its various parts seemed to him but one thing, in like manner as the bodies of the lower world which is subject to generation and corruption, he took a broad view of the whole world, and debated within himself whether it existed in time after it had been, and came to be out of nothing; or whether it was a thing that had existed from eternity and never wanted a beginning.