On the Rain, by Anaxagoras

An exercise in discovery fiction

How does it rain? 

Many believe it rains by the will of Cloud-Gatherer Zeus, the god who by choosing when and where to let down heaven’s water, alone decides whether we reap what we sow, and whether our work will be wasted or fruitful. 

But the following demonstration will show that Zeus himself (as the ancients knew) is subordinate to the forces of necessity; this demonstration will put forth that it is the Sun, and not the king of the gods, which is the main cause of rain—and that the Sun acts not through the intent of Helios or Apollo, but merely through the force of its heat, which has as its source a distant, fiery ball possessed of tremendous power (the nature of which I have discussed elsewhere). 

So let us begin our discussion of rain with the climb, for an ascent always precedes a fall.

It is well-known that a pot of water put to boil will, after a time, empty itself, and that the bubbling water will shimmer into a steam breathed by cooks in the course of their work.  And by the very same principle does the sun in its flaming vigor heat the boundless waters, filling the universal air with a moisture all men can taste. It is in this way that seeds of water arise and are dispersed from their sources—whether from rivers above or below the earth, or the vast oceans—and come to occupy the sky. 

But though I contend here that the Sun is the primary cause of rain, water is not the only seed whose movement it is useful to understand. This is because the heat of the sun also generates wind, which should properly be regarded as the movement of air-seeds.

The generation of wind can be explained as follows: the sun’s heat falls unevenly upon the earth, agitating seeds of air more in some regions than in others. The faster moving air of the heated regions pushes out and crowds into the other areas; if one were to stand in the slower (and cool) regions, one would experience the pushed air as wind. 

The speed-hardened seeds of air then scrape the earth’s surface, causing the smallest seeds of earth (with the weakest ties to ground) to spring up and be borne aloft above the earth, and yes, even far above our heads. (Some may protest that the Lord of the Sky has no communion with the cthonic world— and how waylaid by childhood stories they are! There is everything-in-everything.) 

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Now we have finished our effortless climb, buoyed by a warm and favorable Sun. But how, after this tale of division, can we forge once again the ties which bound such immense parts of nature? How should we try to understand movements like those of earth and air and water, which occur on a scale and remoteness too difficult for steady observation? If only those same entities could be found nearer, to where mortal sense is strongest. 

It is our fortune that in this matter this is just the case. Clouds can, after all, come down from their heavenly bowers, when they are often seen hanging heavy in the slowness of the morning, caught by close sight before remembering to float home. It will also be noticed that such clouds depart having drenched many blades in moisture, having left so much green glistening in the light. It would seem, therefore, that all that is needed to collect seeds of water from their aery wanderings, is nothing but a solid small surface.

And where in the sky is such a solid surface to be found? Is it not in the little grindings of dust, those little seeds of earth borne up by the wind? Just as dew may settle around the blade-points of grass, and the fine tips and needles of our country’s trees, so too does water collect around the seeds of earth pushed up into the sky.

Thus even a raindrop has a mixed nature, and consists of a single seed of earth weighed down, like a trader with his goods, by many more seeds of water. And like many a trader, certainly the rain which falls on Delos does not have its origins in the self-same place, but must have come from somewhere else—though from how far away, precisely, it is not given for mortals to know. Instead of punishing ourselves for our ignorance, however, we may perhaps find pleasure in the thought that by transporting the soil of one place to another, the laughing winds make givers of all lands. 

There may still be those who ask “But in times of excessive heat, why is there no rain? If the sun is the driver of rain, shouldn’t more sun lead to more rain, not less?” It is even likely that those who ask such questions do so out of piety, seeking to recover a place for divinities in the affairs of men. But a reply to the devout is readily found. 

Recall when earlier I suggested that heat has the effect of dispersing seeds of water. It follows, then, that in excess this heat not only disperses the water-seeds, but also keeps them dispersed, and overwhelms the tendency towards collection on a solid surface. 

On occasion, therefore, this excess of heat results in an excess of deprivation: in empty riverbeds, or dry, dusty air which ruins many crops. But this is evidence less of the gods’ displeasure than of the illimitable power of the Sun, which has shined without ceasing for as long as men began to mark its movements. 

I end this demonstration with a last remark: that when reasoning about natural events, we should not be overly concerned with persons acting on persons, as if Zeus commanded the sun to glow or cajoled the earth to accept drops of the sky’s affection. No, the world is rather an assemblage of bodies acting on bodies; it consists of an alternation of growth and dissolution wherein a finite number of indestructible seeds change their proportions within the objects they compose. Mind alone is separate from these seeds and works to comprehend them. But of Mind, no more will I say here. 

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Finally, a note about the form:

This was an exercise in discovery fiction, a term coined by Michael Nielsen to refer to “an idealized literary form for scientific results.” As you just read, the form tries to walk any sufficiently curious reader through a line of reasoning which could plausibly have resulted in a mathematical deduction or scientific discovery.

As soon as I heard of the idea, nerd that I am, I searched my memory for a simple natural phenomenon to which I could apply the form, ideally one formerly vested with supernatural significance whose mechanistic explanation would come off a little…well, naughty. A little subversive humor may, after all, make an altogether abstract or technical piece go down more easily. But of course, humor is just one of many devices.

There are other kinds of aesthetic pleasure we can use to “literarize” technical ideas. In this I felt guided by Lucretius, who put it this way in his sly explanation of why he wrote a philosophical work—on atoms, perception, and the finality of death, among other things—in the form of a lengthy poem:

A cup of bitter medicine with honey on the lip

Just as doctors, when they try to give children foul-tasting wormwood,

first touch the rim around the cup with the sweet, golden liquor of honey,

to trick the children's naive youth just as far as the lips,

so that meanwhile they drink down the bitter wormwood's juice—

the intent is deceptive, but not destructive:

it is restoration of the patients' health that they seek.

On the Nature of Things (1.936-943)

So for this piece of writing I felt I was in need of a character—a mouthpiece, you might say—whose rigorous thought could be offset by a kind of humorous impiety, as well as an inclination for the occasional poetic line. In other words, the piece could not be all head and no heart; it could not be all medicine and no sweetness.

And since I’ve always been interested in “early scientists”—mainly certain pre-Socratics, who were known for some remarkably sound (as well as remarkably unsound) ideas— for my mouthpiece I eventually chose Anaxagoras, who (in)famously developed theories about nature without reference to the gods.

The balancing-act with this piece was that I thought my explanation of “how it rains” shouldn’t be too objectionable either to Anaxagoras, a modern meteorologist, or even a smart fifth grader learning about the weather. I’ve tried to be faithful to Anaxagoras’ original use of the concepts of ‘seeds’ and ‘everything-in-everything’, even as I molded these together, sometimes haphazardly, with current ideas of why the wind blows and how clouds form.

My aim here, I realized, wasn’t to somehow “revise” Anaxagoras (though that’s how I thought when I started doing it). It was to instead ask: would it have been possible for an ancient to conceive of causal interactions in nature similarly to us, but purely within their own system or paradigm?

In a few cases, in fact, it seems like this happened, as when Anaxagoras first correctly explained eclipses as the imposition of a solid body between the sun and earth. But we often consider such cases so rare as to be flukes, since ancient assumptions are so different from our own. It may therefore be tempting to consider ancient paradigms totally “incommensurate”, with ours (as some have done), and leave it at that, but this now seems rather unsatisfying to me.

Why do some thinkers have more of these “flukes” than others? I don’t much like answers that say something like “oh, they were influential”—that the mere lasting influence of these thinkers is what kept their ideas persisting through till current models. But why were they influential? We have to ask: what if they were onto something real and correct?

It instead now seems to me like such thinkers were groping, with the language available to them, toward explaining things they actually observed—and that we can still observe—and so that to say they were doing something completely different from us would be to unduly estrange one period of human thinking from another.

Might “discovery fiction” be a way of experimenting with scientific frameworks? What ideas are we failing to piece together with the tools right in front of us, ideas which some future civilization may want to run “discovery fiction” on us for? It’s my hope that pieces like this one will get us part-way to some answers.