Here likewise Scripture says, in accordance with what I said above, “And God called the firmament Heaven” (Gen. i. 8), in order to explain the homonymity of the term shamayim (heaven), and to show that shamayim in the first verse is not the firmament which is also called shamayim (heaven). The difference is more clearly expressed in the words, “In the open firmament of heaven” (ibid. i. 20); here it is shown that “firmament” (rakiʻa), and “heaven” (shamayim), are two different things. In consequence of this homonymity of the term shamayim the term rakiʻa (firmament) is also used of the true heaven, just as the real firmament is sometimes called shamayim (heaven); comp. “And God set them in the rakiʻa (firmament) of the heaven” (ibid. i. 17). This verse shows clearly that the stars, the sun, and the moon are not, as people believe, on the surface of the spheres, but they are fixed in the spheres, and this has been proved satisfactorily, there being no vacuum in the Universe; for it is said, “in the firmament of the heaven,” and not “upon the firmament of the heaven.” It is therefore clear that there has been one common element called water, which has been afterwards distinguished by three different forms; one part forms the seas, another the firmament, and a third part is over the firmament, and all this is separate from the earth. The Scriptural text follows here a peculiar method in order to indicate some extraordinary mysteries. It has also been declared by our Sages that the portion above the firmament is only water by name, not in reality, for they say (Babyl. Talmud, Ḥagigah 14b) “Four entered the paradise,” etc. R. Akiba said to them, “When you come to the stores of pure marble, do not say, Water, water, for it is written, ‘He that telleth lies shall not tarry in my sight’” (Ps. ci. 7). Consider, if you belong to the class of thinking men, how clearly and distinctly this passage explains the subject for those who reflect on it! Understand that which has been proved by Aristotle in his book On Meteorology, and note whatever men of science have said on meteorological matters.