Lecture 1 — Aristotle's intent in this book; enumeration of ground previously covered in preceding books and yet to be covered in subsequent books

We have already discussed the first causes of nature, and all natural motion, also the stars ordered in the motion of the heavens, and the physical elements—enumerating and specifying them and showing how they change into one another—and becoming and perishing in general.

There remains for consideration a part of this inquiry which all our predecessors called meteorology.

It is concerned with events that are natural, though their order is less perfect than that of the first of the elements of bodies. They take place in the region nearest to the motion of the stars. Such are the milky way, and comets, and the movements of meteors.

It studies also all the affections we may call common to air and water,

and the kinds and parts of the earth and the affections of its parts. These throw light on the causes of winds and earthquakes and all the consequences the motions of these kinds and parts involve. Of these things some puzzle us, while others admit of explanation in some degree.

Further, the inquiry is concerned with the falling of thunderbolts and with whirlwinds and fire-winds, and further, the recurrent affections produced in these same bodies by concretion.

When the inquiry into these matters is concluded let us consider what account we can give, in accordance with the method we have followed, of animals and plants, both generally and in detail. When that has been done we may say that the whole of our original undertaking will have been carried out.

1. Just as in natural things nothing is perfect so long as it is in potency, but is perfect absolutely only when it is in ultimate act, and just as, when it is midway between pure potency and pure act, it is perfect in a qualified sense but yet not absolutely so too with science. Now the science which one has of a thing only in a universal way is not science complete according to ultimate act, but is midway between pure potency and ultimate act. For someone who knows something in a universal way, does indeed know something in act of the things that are included in its proper notion; but he who thus knows in a universal way, knows other things, not actually, but in potency only. For example, one who knows man only accordingly as he is animal, thus knows in act only a part of the definition of man, namely, the genus; but the differences constitutive of the species he does not yet know in act but potentially only. Consequently, it is plain that the completion of science requires that one not stop at what is common but go on to the species (individuals not falling under the consideration of art, since of them there is not intellectual understanding but sense knowledge).

2. For this reason, since Aristotle in the book, On Generation, has determined concerning the transmutation of elements in common, it was necessary, for the completion of natural science, to determine concerning the species of transmutations that affect the elements. And he determines concerning these in this book, entitled Meteorology. It is his intention, therefore, in this book to determine concerning the transmutations that occur with respect to the elements, according to their several species. And in order to indicate his intention he presents an introduction, in which he does three things:

first, he enumerates the things already treated in the books of natural science that precede this book;

second, he shows what is to be treated in this book, at there remains for consideration (338a25);

third, he shows what remains to be discussed in books that follow, at when the inquiry into these matters (339a5).

3. Three books precede the present one, according to order, in natural science. Hence he does three things.

First, he states what was treated in the book of Physics. As to the first two books, it is question of the causes of nature. This he alludes to, concluding from what has been determined in the books preceding [the Meteorology], when he says: we have already spoken about the first causes of nature, meaning by first causes of nature, the first principles, which are matter, form and privation, as well as the four genera of causes, namely, matter, form, agent and end. In the subsequent books of the Physics the discussion is of motion in general; hence he adds, and of every natural motion.

The second book of natural science is the book, On the Heavens, in the first part of which, i.e., in its first two books, the discussion is about the heaven and the stars, which are moved with circular motion. This he alludes to when he says: we have also discussed the superior movement of the well-appointed stars, meaning by well-appointed, very beautifully arranged, and by as to their superior motion, the circular motion by which all the heavenly bodies are moved.

In the second part of that book, i.e. in the third and fourth books, he determines concerning the number of elements and their local motion. Alluding to this he says: and about the bodily elements we have discussed their number and nature. He says bodily elements to distinguish them from the first principles, namely, matter and form, which are not bodies but the elements or principles of bodies, whereas fire and water and earth are bodies, and are the elements of other bodies.

The third book of natural science is the book, On Generation, wherein are treated the mutual transmutation of elements, in the second book; and generation and corruption in common, in the first book. This he subsequently alludes to when he says, and of things that are mutually transmutable.

4. Then when he says, there remains for consideration (338a25), he shows what is to be discussed in the present book. About this he does two things:

first, he gives the usual name for this body of doctrine;

second, he enumerates the things contained in this doctrine.

He says therefore first that the remaining part of this method, i.e. of natural science, which we have before us, is still to be treated. [What is now to be considered] is what all the earlier philosophers called meteorology—from meteoron which means "on high" or "elevated," and from logos, which is a "statement" or "explanation"—for in it are considered the things generated on high, such as falling stars, comets, rain, snow, and so on. This does not mean that other things, produced in the lower regions, such as lightning, earthquakes and the like, will not be discussed; but, because things generated on high are more marvelous and more desired, it is from them that this whole doctrine takes its name.

5. second, at it is concerned (338a26), he enumerates the things to be considered in this doctrine. These are seen to be divided into four groups. For there are some things that are produced in the highest region, nearest to the heavenly body. Such things are, namely, those concerning which it still remains to be considered, things that happen indeed according to nature, but not an ordered nature and, as some claimed, by chance. This more irregular nature is not, however, the nature which belongs to the first element of bodies, i.e., the celestial body, called element, because it is a part of the whole corporeal universe, although it does not enter into the composition of mixed bodies, as do the elements. The nature according to which these things occur is more unordered than the nature of the celestial body, since the things in the celestial body always behave in the same way, whereas in the transmutations affecting the lower bodies much variation occurs. It was on this account that some have believed that these occurred, not by nature, but by chance, failing to consider that there is produced by nature, not only those things which happen always, but also those which happen for the most part. These, I say, occur in the region nearest the carrying of the stars, i.e., the stars that are circularly moved. This he sets down to distinguish them from those that follow. As an example he mentions the milk, i.e., the milky circle called the "galaxy," and the stars called comets, and the phantoms, i.e. the apparitions, fiery and moving, called "falling stars" [meteors].

6. second when he says, it studies also (338b24), he enumerates the things which take place under the foregoing; namely, all things that are posited as phenomena common to air and water—for they are produced from aqueous matter in the region of air, when vapors are changed into water.

7. third when he says, and the kinds and parts of the earth (338b25), he enumerates what takes place in the lowest region and says: we must also talk about the parts of the earth, such as east, west, north, south, and about its kinds, for example, that some earth is hot and sandy, and some cold and compact, and about the properties of the parts of the earth, for example, that some are sulphurous, some stony or in some way broken up. From this knowledge of the earth we shall consider all the causes of spirits, i.e., winds, that differ according to the difference of the earth. Likewise, of earthquakes, the causes of which are attributed to the different type of earth, and of all things that take place according to the motions of these, i.e., of winds and earthquakes. In these matters we cannot explain everything perfectly and according to certitude, but shall let some things remain doubtful, giving reasons for both sides; but in others we shall to some degree reach the truth.

8. Fourth, at further, the inquiry is concerned with the falling of thunderbolts (339a3), he enumerates the things which descend from on high as the result of winds. He says, therefore, that we shall also give an account of the falling of thunderbolts, and of whirlwinds (called siphons) and of the burnings that accompany such whirlwinds, and of other circular phenomena that occur from congealing and are properties of those bodies, namely, the elements. He says this because whirlwinds are generated from compacted matter set rotating, and many other like things happen to whirlwinds as a result of matter compacted and set in circular motion. Or this could refer to the rainbow and halo (i.e., the corona surrounding the sun and moon and stars) which result from rays rebounding from thick matter.

9. Then when he says, when the inquiry into these matters (339a5), he mentions what remains to be treated in the books to follow and says that after we shall have finished with these matters enumerated above, we shall to the best of our ability, according to the method employed in earlier books (i.e., not by merely reciting others' opinions, but by inquiring into causes, speculate about animals and plants, both in a universal way and according to the individual species. And that will be almost the end of the natural science which we chose to discuss from the beginning. He says almost, because not all natural things can be known by man.