Lecture 11 — The nature of odor

Odors must be understood in the same way. For what dryness causes in moistness, enchymous moistness causes in another genus, namely air, and water as well.

We now call what is common in these the transparent. But this is an object of smell not according as it is transparent, but according as it is capable of being soaked or cleansed by enchymous dryness.

The odorous is not only in air, but also in water. This is clear in the case of fish and testacea, for they seem to smell. And air does not exist in water, for it floats to the top when it is in water. And these animals do not breathe.

Accordingly, if one holds that water and air are both moist, odor will be the nature of enchymous dryness in moisture, and the odorous is what is such.

That this affection is caused by the enchymous is clear both from what has and from what does not have odor. For the elements, namely, fire, air, earth, and water, are odorless, because both the dry and the moist ones are achymous unless a mixture is made. This is why the sea has odor, for it has moisture and dryness. And salt is more odorous than niter (the fact that oil flows out of these is revealing), but niter has more earth.

Moreover, a stone is odorless, for it is achymous. But woods are odorous, for they are enchymous, and those that are watery are less odorous.

Moreover, among metals, gold is odorless, for it is achymous. Brass and iron are odorous, but when the moisture is burned out of them, their slag is made odorless. Silver and tin are more odorous than some, but less than others, for they are watery.

Now it seems to some that odor is a smoky evaporation, and that this is common to earth and air. They all speak of odor on this basis. Thus Heraclitus says that if all beings became smoke, the nostrils would discern them. They all introduce some such cause of odor, some presenting it as an “exhalation,” some as an “evaporation,” and some as both of these. Vapor is a kind of moisture, but smoky exhalation, as was said, is something common to air and earth. Water is produced from the former, but a kind of earth from the latter.

But odor seems to be neither of these, for vapor belongs to water, but smoky evaporation cannot occur in water. For animals in water also smell, as was said above.

Moreover, they use the term “evaporation” as they do the term “emanations.” Therefore, if the latter is not correct, neither is the former.

Therefore it is not hard to see that moisture—both that in wind and that in water—can receive and be affected in some way by enchymous dryness. For air too is by nature moist.

Moreover, if this produces in what is moist and in air something like dryness that has been soaked, it is clear that odors must be analogous to moistures.

And in some cases they are so, for odors are also “sour” and “sweet” and “harsh” and “pungent” and “rich.” And one might say that what is putrid is analogous to what is bitter: as the latter is difficult to drink, what is putrid is dysanapneustic. It is clear, then, that what flavor is in water, odor is in air and water.

For this reason cold and cohesion make flavors dull and drive out odors: for cold and cohesion remove the heat that moves and generates them.

162. Odors must be understood in the same way (442b27). After the Philosopher has made a determination about flavors, here he begins to make a determination about odors. This is divided into two parts.

In the first, he makes the determination about odors.

In the second, he compares the sense of smell to the other senses, where he says the senses exist in an odd number (445a4; [200]).

On the first point, he does two things.

First, he determines the generation and the nature of odor.

Second, he determines the species of odor, where he says there are two species of the odorous (443b16; [177]).

On the first point, he does two things.

First, he shows what is passive in the generation of odors.

Second, he shows what is active in it, where he says that this affection is caused by the enchymous (443a8; [166]).

On the first point, he does three things.

First, he presents his intention.

Second, he explains something he said, where he says we now call what is common (442b29; [163]).

Third, he proves it, where he says the odorous is not only in air (443a2; [164]).

Accordingly, he first says that the generation of odors must be understood in the same way as that of flavors: that is, there is something passive and something active. What was said about flavors was that the moistness of water is affected by the dryness of earth, and thus is brought by the action of heat to the condition of being flavored. (Cf. ch. 9, nn. 133–34.) But what is active in the generation of odor is enchymous moistness. It is called enchymous from “en,” which means “in,” and “chymous,” which means “moisture”: for the moisture exists as, so to speak, drunk in by and incorporated into something dry. This, then, is what is active in odor. What is passive is another genus that includes air and water.

163. Then when he says we now call what is common (442b29), he explains what this genus is that is common to air and water and is receptive of odor.

He says that what is common to the two is called the transparent. However, the transparent as transparent is receptive not of odor, but of color, as was established above: (1.3, 439a18–b14; cf. ch. 5, nn. 86, 90–92; ch. 6, n. 95; ch. 7, n. 115.) but it is receptive of odor according as it is capable of being soaked or cleansed by enchymous dryness, that is, according as it is receptive of enchymous dryness. He calls this reception a “soaking” or a “cleansing” inasmuch as a thing is naturally washed or cleansed by the moisture it receives.

164. Then when he says the odorous is not only in air (443a2), he proves something he presupposed, namely that not only air but also water is receptive of odor.

First, he introduces a proof of this.

Second, he concludes to what is properly receptive of odor, where he says accordingly, if one holds that water and air (443a6; [165]).

Accordingly, he first says that odor is received not only in air, but also in water. This is clearly shown by the fact that fish and testacea—that is, hard-shelled animals that live in water—seem to smell from the fact that they are attracted from a distance by odor to food they cannot see. From this it is clear, by two arguments, that water is receptive of odor.

First, these animals live not in air but water. And he proves that there is no air under water, where fish of this kind live, by the fact that air floats to the top of water even if it is put underwater. This is evident in the case of an inflated bag, which, if submerged by force, will float to the surface of the water.

Second, even granting that there is air under water, nevertheless such animals do not breathe air. Therefore, if only air were receptive of odor, they would not perceive odor.

165. Then, when he says accordingly, if one holds that water and air (443a6), he concludes to what is properly receptive of odor. He says that because air and water, which are receptive of odor, are moist, it follows that odor is nothing but the “nature”—that is, the form—impressed by enchymous dryness on the moisture that is air and water. And the odorous is what is such: that is, moisture with a “nature” impressed on it by enchymous dryness.

166. Then, when he says that this affection is caused by the enchymous (443a8), he proves that the enchymous causes odor. He proves this in three ways:

first by what has and what does not have odor;

second, where he says now it seems to some (443a21; [169]), by different opinions some have held about odor;

third, where he says moreover, if this produces (443b6; [174]), by the affinity of odor with flavor.

Accordingly, he first says that it is clear, both from what has and from what does not have odor, that this affection that is odor is impressed by the enchymous—that is, by moistness instilled in and absorbed by dryness, as was said above (442b27; [162]).

First, because all the elements, namely fire, air, water, and earth, lack odor. For whether they are moist or dry, they are achymous—that is, without moisture absorbed by dryness—for those that are moist have moistness without dryness, and those that are dry have dryness without moistness. This is the case unless a mixture of elements is made. Thus the sea has an odor, because dryness of earth has been mixed into moisture of water in it, as is clear from its salty flavor: for salt has even more odor than does niter. And that these two—salt and niter—do have something of the enchymous, is clear from the oil that is brought out of them by means of a certain technique, which shows that there is in them an oily moisture absorbed by dryness. But niter has less of this moisture than does salt, and so is less odorous.

167. Second, he shows the same thing in the case of stones and woods. He says that a solid and hard stone lacks odor because, due to its great component of earth, it does not have the odor-causing moisture mentioned. But woods do have odor because they do have something of the moisture mentioned, as is clear from the fact that they are inflammable because of an oiliness that exists in them. Hence woods that have a more watery and less oily moisture—one that is not absorbed, as it were, by dryness—are less odorous. This is clearly the case with poplar wood. But fir and pine woods are very odorous because of the oiliness of their moisture.

168. Third, he shows the same thing in the case of metals, among which gold is completely odorless, because it lacks the moisture mentioned; this is due to its large component of earth, which is indicated by its very great weight: for it is heavier than other metals. Brass and iron are odorous, because the moisture in them is digested and drunk in by the dryness, but not wholly overcome by it, as it is in the case of gold; hence their slag is less odorous because of the burning off of the moisture in them. Silver and tin are more odorous than gold, but less than brass and iron: for they have a moisture that is more watery and less absorbed by dryness than do brass and iron; however, because their moisture is in a way absorbed by dryness, they are not completely odorless like gold.

169. Then, when he says now it seems to some (443a21), he shows that the enchymous is what is active in odor through opinions of others. On this point, he does three things.

First, he presents the opinions of the others.

Second, he eliminates them, where he says but odor seems to be neither of these (443a29; [171]).

Third, he concludes to his proposal, where he says therefore it is not hard to see (443b3; [173]).

Accordingly, he first says that it seems to some that odor is a smoky evaporation, smoke being common to air and earth, i.e., an intermediary between them, as it were, because it is something dissolved from dryness of earth that does not achieve the fineness of air. All of the ancients speak of odor in a way close to this position. Hence Heraclitus says that if all beings were dissolved into smoke, the nostrils, in perceiving odor, would discern all beings, as if to say that all beings would be odors. For Heraclitus thought that vapor is a principle of things.

170. But not all philosophers held that odor is smoke; some held that it is just something like it. Therefore, in order to show this diversity, he adds that some assigned “exhalation” to odor, some “evaporation,” and some both. And he shows the difference between these two: evaporation is nothing but dissolved moisture of water, but exhalation or smoke is something common to air and earth, since it is something dissolved from dryness of earth, as was said (443a12). (Cf. ch. 8, n. 118.) A sign of this difference is that when vapor is condensed, water is generated from it, but when exhalation of smoke is condensed, something earthen is generated from it.

171. Then, when he says but odor seems to be neither of these (443a29), he eliminates the above-mentioned positions by two arguments.

The first is that vapor pertains to water, which is not odorous without an admixture of dryness, as was said above (443a9–12). But smoke cannot occur in water, although odor does occur in it, as was shown above by the fact that some animals can smell in water. Therefore odor is neither smoke nor vapor.

172. Then, when he says moreover, they use the term “evaporation,” (443b1) he presents the second argument. It is this. The argument that odor should be called an “evaporation” is similar to the argument that colors should be called “emanations.” But, as was shown above, the latter is not a correct description of colors; (1.3, 440a15–20; cf. ch. 7, nn. 105–7.) therefore, neither is the former a correct description of odors.

For in both cases it would follow that sensing occurs through contact, whether of the odors or of the colors, and that bodies seen and smelled are diminished and finally completely dissolved by the emanation or dissolution. And this is unreasonable, especially since a thing can be seen and smelled from such a distance that there is no way that something dissolved from the body could be carried that far. Rather, perception of both color and odor occurs at such distance through a spiritual alteration of the medium.

173. Then, when he says therefore it is not hard to see (443b3), he concludes to the proposal, namely that, because odor is neither vapor nor smoke, it is clear that moisture in “wind”—that is, air—and water is affected by enchymous dryness, and thus odor occurs and is perceived. For moisture is present not only in water, but also in air.

174. Then, when he says moreover, if this produces (443b6), he shows that the enchymous is what is active in odor by the affinity of odor with flavor. On this point, he does three things.

First, he presents the proposal. He says that if the enchymous causes odor in the moisture of water and air, in the way that the dryness of earth soaked by the moisture of water causes flavors, it is clear that odors must be analogous to flavors.

175. Second, where he says and in some cases (443b8), he clarifies the proposal by coordinating odors with flavors.

He says that in some cases this coordination is evident. For odors are called “sour” and “sweet” and “harsh”—that is, astringent—and “pungent” and “rich,” just like flavors. But we do not call odors “bitter”: rather, putrid odors correspond analogously to bitter flavors, for just as bitter flavors are swallowed with difficulty, so what is putrid is “dysanapneustic”—that is, difficult to inhale. Hence it is clear from this affinity of odor with flavor that flavor occurs in water in the way that odor occurs in air and water.

176. Third, where he says for this reason (443b14), he proves the abovementioned affinity through impediments to flavor and odor. Flavors are made dull, and odors are driven out, by cold and freezing, inasmuch as the heat that generates and moves odors and flavors is removed by cold and freezing, as is clear from what was said. (1.4, 441b8–442a12; cf. ch. 9, n. 144.)