i.e., It is evident that it is not by their taste or by their odour that the natures of natural bodies are known, for if they were recognised by their colours, all white bodies would have the same nature, and everything of the same colour or taste would be of the same nature; for we see that snow and dough (?) and fresh cheese have the same colour although each of them has a different nature. We see again that, although parsley and aloes agree in pungency, they are not of the same nature since one is sharp and the other mild; and in the same way we speak of smell. Consequently, not by their taste or smell or touch, is the nature of the natural bodies known, but by their positions and motions. The ill-informed declare that the firmament changes in parts, or in its own entirety, with length of time, although that change is not apparent to us, as we see gold, iron, the body, jacinth and many other precious stones becoming discoloured (?) with age and length of time, and changing in size, colour, taste and smell with length of time, although we are not aware of that change when it is in progress, on account of the great extent of time during which it is carried on.
I say to them in answer, that everything that is beneath the moon in the sphere of the four elements undergoes change, and that change is of two kindscomplete and partialand those two changes concern growth and decay, and the complete change is more 'evident than the partial. Every body
Thus if the firmament were increased or decreased, its actions would manifest that change to us. For were it augmented and extended, and the constellations placed further from us than they are, we should see then a smaller quantity of them than we do now observe, and there are many of them which we see now, that we should not see then. Consequently, when it would have closed in around the earth, the quantity of the stars would seem to us more prodigious then than now, and then we would see many stars that we did not see before. Now, since no one ever has seen these changes in the firmament (for if he had, it would be found written) it is sure and certain, that the firmament suffers neither increase or decrease, and is neither narrowed nor widened.
Similarly if the firmament inclined to its right or to its left, or forwards or backwards, or if it moved up or down from the position in which it is, the centre, i.e., the earth, must necessarily change with it but the earth cannot leave its own position, since it has no place to go; for