Epicurus, Letter to Herodotus 46-7 and 62

This text by the Hellenistic philosopher Epicurus is a brief summary of his physics. Epicurus was an atomist who believed the universe was made of tiny, invisible, irreducible elements that are always in motion and travel at a constant, inconceivably fast velocity even after colliding with one another. Conglomerates of these atoms make bodies. Bodies cannot move at atomic speed, though their atoms still do by vibrating. Bodies also slow down when they collide. We can perceive bodies because they emit incredibly thin images of themselves at all times. The incredibly thin images, called idols, reach us in this way:

καὶ μὴν καὶ ἡ διὰ τοῦ κενοῦ φορὰ κατὰ μηδεμίαν ἀπάντησιν τῶν ἀντικοψόντων γινομένη πᾶν μῆκος περιληπτὸν ἐν ἀπερινοήτῳ χρόνῳ συντελεῖ. βράδους γὰρ καὶ τάχους ἀντικοπὴ καὶ οὐκ ἀντικοπὴ ὁμοίωμα λαμβάνει. (46)

Moreover, in the absence of any collision, the idols’ voyage through the void will cross any conceivable distance in an imperceptible amount of time. Because here collision or freedom from collision are like slowness and speed.

What this means is that an idol that allows us to perceive a body can travel at atomic speed, i.e. can instantaneously reach us for all intents and purposes so there is no lag in our perception. But Epicurus specifically explains here that an idol can go slower than atomic speed, meaning there would be a lag.

The passage that follows has confounded scholars, but I think its meaning is explained by this last point. I will quote the Greek passage first and then the various different translations over the decades to give an idea of how controversial and challenging the language here is.

Οὐ μὴν οὐδ᾽ ἅμα κατὰ τοὺς διὰ λόγου θεωρητοὺς χρόνους αὐτὸ τὸ φερόμενον σῶμα ἐπὶ τοὺς πλείους τόπους ἀφικνεῖται — ἀδιανόητον γάρ,– καὶ τοῦτο συναφικνούμενον ἐν αἰσθητῷ χρόνῳ ὅθεν δήποθεν τοῦ ἀπείρου οὐκ ἐξ οὗ ἂν περιλάβωμεν τὴν φορὰν τόπου ἔσται ἀφιστάμενον: ἀντικοπῇ γὰρ ὅμοιον ἔσται, κἂν μέχρι τοσούτου τὸ τάχος τῆς φορᾶς μὴ ἀντικόπτον καταλίπωμεν. (47)

At all events, a body in motion does not find itself, at any moment imaginable, in two places at the same time; that is quite inconceivable. From whatever point of infinity it arrives at some appreciable moment, and whatever may be the spot it its course in which we perceive its motion, it has evidently quitted that spot at the moment of our thought; for this motion which, as we have admitted up to this point, encounters no obstacle to its rapidity, is wholly in the same condition as that the rapidity of which is diminished by the shock of some resistance. (C.D. Yonge)

Not that, if we consider the minute times perceptible by reason alone, the moving body itself arrives at more than one place simultaneously (for this too is inconceivable), although in time perceptible to sense it does arrive simultaneously, however different the point of departure from that conceived by us. For if it changed its direction, that would be equivalent to its meeting with resistance, even if up to that point we allow nothing to impede the rate of its flight. (R.D. Hicks)

On the other hand, a moving body cannot arrive at several places at once in the shortest conceivable period of time. That is unthinkable. But when in a perceivable period of time a body arrives along with others from some point or other in the infinite, the distance covered will be extraordinary. If it were otherwise, collisions would have been involved – though we still allow some limit to speed of motion as a result of non-collision. (Erik Anderson)

By no means, in any case not in time measured in thinkable units, does a body in motion arrive at several places at once – because that is unthinkable –, and when it arrives within a perceptible unit of time from anywhere in space, at that very moment the body will not have moved from the spot where we perceive it be to begin with. Because that would be similar to collision, even if we allow the speed of the body’s motion to be as fast as it would be without collision. (Hans-Wolfgang Krautz, my translation from the German)

And finally in an article in Classical Philology, Vol. 36, No. 4 (Oct., 1941) specifically on this passage, Norman W. Dewitt concluded this was the correct translation:

It certainly must not be thought, however, that the moving mass also arrives at the same time at the greater distances in units of time discernible only by reason, for it is unthinkable, and this [the moving mass], arriving suddenly at a perceptible moment out of the infinite [that is, out of the invisible], will be inseparable from the spot where we shall first discern the motion, for it [the fact of its becoming visible] will be equivalent to retardation, even if down to this point we leave the velocity of the motion unimpeded.

Without even trying to understand what errors these translators made, it’s clear with the exception of Dewitt’s translation that none of them actually make any logical sense in English at all, and Dewitt’s translation is simply too far from the original Greek to be accurate (e.g. ἐπὶ τοὺς πλείους τόπους cannot mean “at greater distances” and must mean “at several places”, which does not fit his argument). It’s also clear that there are several words and phrases that are the chief cause the problem: κατὰ τοὺς διὰ λόγου θεωρητοὺς χρόνους, “in time perceived by reason”, συναφικνούμενον “arriving together” (this word appears only here in all extant Ancient Greek texts, i.e. a hapax legomenon), and ἐν αἰσθητῷ χρόνῳ, “in perceptible time”. No translator has managed to reconcile the idea of an object arriving at several places at once with the previous discussion of idols and then the final mention of collision.

My solution is this: Epicurus specifically sets up a contrast in 46 between slow and fast idols. The next section, 47, explains the consequences of slow idols. If an airplane is moving across the sky, and light from the plane (in the form of an idol) meets my eye without any obstruction, then I see the plane at exactly the place where it actually is, because the idol travels at a speed so inconceivably fast there is no delay. But if at a moment previously an idol emitted by the same plane was slowed by a collision, that idol might reach me (or another observer) at the same time as the later, unobstructed idol. Then it would seem that the plane is in two places at once – where the faster later idol shows it to be and the slower previous idol. So this is why Epicurus affirms that a body can arrive at two places at once (συναφικνούμενον) but only in “perceptible time” (ἐν αἰσθητῷ χρόνῳ). That it arrives at two places at once in time perceived by reason (κατὰ τοὺς διὰ λόγου θεωρητοὺς χρόνους) or in actual reality since time perceived by reason is the smallest unit of time in the universe, is, according to Epicurus, “unthinkable” or “inconceivable” as all have translated those words in the sentence.

The words in the last phrase that have caused the most confusion are “τὸ τάχος τῆς φορᾶς” or “the speed of the motion”. Translators have overlooked the difference between “φορὰ” which means motion or path of motion, and the other words Epicurus uses to describe the place where a body is at one moment. Taking that into account, it appears the last phrase here just establishes that even if we see a body in two places at once, that doesn’t mean that in between those two places the body took any other path than the one we would imagine, which is shown in A in the illustration here:

Epicurus means that the path the body takes will be the one we should perceive in the absence of a distortion of our perception, if we assume there has not been any collision in between. In other words, just because our perception misses some part of the trajectory doesn’t mean the body’s trajectory is entirely uncertain, as in B in the illustration.

Finally, looking at a related passage that has caused similar problems, I think the conclusions above help unravel the meaning there too. After explaining that even though composite bodies move at different speeds, the atoms within them do not due to vibrating atomic motion, Epicurus concludes:

τὸ γὰρ προσδοξαζόμενον περὶ τοῦ ἀοράτου, ὡς ἄρα καὶ οἱ διὰ λόγου θεωρητοὶ χρόνοι τὸ συνεχὲς τῆς φορᾶς ἕξουσιν, οὐκ ἀληθές ἐστιν ἐπὶ τῶν τοιούτων: ἐπεὶ τό γε θεωρούμενον πᾶν ἢ κατ᾽ ἐπιβολὴν λαμβανόμενον τῇ διανοίᾳ ἀληθές ἐστι. (62)

This passage is central to understanding Epicurus, because many commentators have taken it as a credo, translating for example:

For the assumption that beyond the range of direct observation even the minute times conceivable by reason will present continuity of motion is not true in the case before us. Our canon is that direct observation by sense and direct apprehension by the mind are alone invariably true. (R.D. Hicks)

Dewitt has rightly contested that approach and in fact shown the clause means close to the opposite:

…for the gratuitous inference of opinion concerning the unseen, that naturally units of time discernible only through reason will also be characterized by motion in a straight line, is not true of such things [as atoms endowed with motion]; because, of course, it is the universe of atoms and void as viewed by reason or received by intuition through the intellect that is true.

As in 46-7, Epicurus is stressing that sometimes our senses deceive us, and what we understand about the atomic world using reason alone is more accurate. So sometimes a body appears to the senses to be in two places at once, but reason perceives that is false. Or we see a body moving faster than another body in space, but the atoms we cannot see that compose these bodies are in fact moving at exactly the same speed in a variety of directions.

Interpreting these passages as I have shows that Epicurus believed there were two ways to perceive the universe, with the senses and with reason. With the senses, we have to rely on idols to get information about the universe. So essentially, knowledge by reason is knowledge about the universe without idols. But then how would we ever get this knowledge? How could reason ever approach the things themselves when our only contact with them is through idols?

For Epicurus, there is simply a division between the “thinkable” and the “unthinkable”. What is thinkable is knowable, even without perception or idols. What is unthinkable is knowable too – in the sense that it is known not to be possible. In this sense, I think epicurean epistemology is impressively cohesive, presenting a self-consistent system. But it leaves open a wide area for disagreement on what we define as the thinkable. In conclusion, here are my translations of the two passages above based on my analysis:

Moreover, in the absence of any collision, the idols’ voyage through the void will cross any conceivable distance in an imperceptible amount of time. Because here collision or freedom from collision are like slowness and speed. But in time perceivable by reason, a body in motion will not arrive at more than one place at once, because that is inconceivable. And although in perceptible time a body can arrive from anywhere in space at more than one place at once, the body will not be elsewhere than where we perceive its path to be, if we allow the motion of its voyage to be free from collision up to that point. (46-7)

So this assumption that the body’s motion at the atomic level is continuous in the same way as its motion in perceptible units of time is not the truth in such cases; because the truth of the universe is perceived either with intuition or by the understanding. (62)

Advertisement