On the Principle of Cold (8-11)

Perhaps we should now leave the question whether heat and cold are substances; if so, let us advance the argument to the next point and inquire what sort of substance coldness has, and what is its first principle and nature. Now those who affirm that there are certain uneven, triangular formations in our bodies[*] and that shivering and trembling, shuddering and the like manifestations, proceed from this rough irregularity, even if they are wrong in the particulars, at least derive the first principle from the proper place; for the investigation should begin, as it were from the very hearth,[*] from the substance of all things. This is, it would seem, the great difference between a philosopher and a physician or a farmer or a flute-player; for the latter are content to examine the causes most remote from the first cause, since as soon as the most immediate cause of an effect is grasped - that fever is brought about by exertion or an overflow of blood, that rusting of grain is caused by days of blazing sun after a rain, that a low note is produced by the angle and construction of the pipes - that is enough to enable a technician to do his proper job. But when the natural philosopher sets out to find the truth as a matter of speculative knowledge, the discovery of immediate causes is not the end, but the beginning of his journey to the first and highest causes. This is the reason why Plato and Democritus,[*] when they were inquiring into the causes of heat and heaviness, were right not to stop their investigation with earth and fire, but

to go on carrying back sensible phenomena to rational origins until they reached, as it were, the minimum number of seeds.

Nevertheless it is better for us first to attack things perceptible to the senses,in which Empedocles[*] and Strato[*] and the Stoics[*] locate the substances that underlie the qualities, the Stoics ascribing the primordially cold to the air, Empedocles and Strato to water; and someone else may, perhaps, be found to affirm that earth is the original substance of coldness.[*] But let us examine Stoic doctrine before the others.

Since fire is not only warm but bright, the opposite natural entity (they say) must be both cold and dark: as gloomy is the opposite of bright, so is cold of hot. Besides, as darkness confounds the sight, so cold confuses the sense of touch. Heat, on the other hand, transmits the sensation of touching, as brightness does that of seeing. It follows, then, that in nature the primordially dark is also the primordially cold; and that it is air which is primordially dark does not, in fact, escape the notice of the poets since they use the term air for darkness:

Thick air lay all about the ships, nor could

The moon shine forth from heaven.[*]

And another instance:

So clad in air they visit all the earth.[*]

And another:

The air at once he scattered and dispelled the mist;

The sun shone forth and all the battle carne in view.[*]

They also call the lightless air knephas, being as it were, kenon phaous void of light; and collected and condensed air has been termed nephos cloud because it is a negation of light.[*] Flecks in the sky and mist and fog and anything else that does not provide a transparent medium for light to reach our senses are merely variations of air; and its invisible and colourless part is called Hades and Acheron.[*] In the same way, then, as air is dark when light is gone, so when heat departs the residue is cold air and nothing else. And this is the reason why it has been termed Tartarus because of its coldness. Hesiod[*] makes this obvious when he writes murky Tartarus; and to shake and shiver with cold is to tartarize. [*] Such, then, is the reason for these names.

Since corruption, in each case, is a change of the things that are corrupted into their opposites, let us see whether the saying holds good that the death of fire is the birth of air. [*] Fire, indeed, perishes like a living creature,[*] being either extinguished by main force or dying out of itself. Now if it is extinguished, that makes the change of fire

into air more conspicuous. Smoke, in fact, is a form of air, as is reek and exhalation, which, to quote Pindar,[*]

Stabs at the air with unctuous smoke.

Nevertheless, even when fire goes out for lack of nourishment, one may see, as for instance in the case of lamps, the apex of the flame passing off into murky, dusky air. Moreover, the vapour ascending from our bodies when, after a bath or sweat, cold water is poured on them, sufficiently illustrates the change of heat, as it perishes, into the air; and this implies that it is the natural opposite of fire. From this the Stoics drew the conclusion that air was primordially dark and cold.

Moreover, freezing, which is the most extreme and violent effect of cold in bodies, is a condition of water, but a function of air. For water of itself is fluid, uncongealed and not cohesive; but when it is compressed by air because of its cold state, it becomes taut and compact. This is the reason for the saying[*]

If Southwind challenges North, instantly snow will appear.

For after the Southwind has collected the moisture as raw material, the Boreal air takes over and congeals it. This is particularly evident in snowfields: when they have discharged a preliminary exhalation of air that is thin and cold, they melt.[*] Aristotle[*] also declares that whetstones of lead will melt and become fluid in the wintertime through excess of cold when no water is anywhere near them; it seems probable that the air with its coldness forces the bodies together until it crushes and breaks them.[*]