Epicurus' On Nature, Books 10, 11 and 12

  • I am currently re-reading Les Epicuriens on the train on my way to/from work, and in the process of trying to imagine or re-construct what these lectures or discussions consisted of as far as possible, so that we can create modern dialogues around these issues to replace the literature that is missing.

    Book 10

    Discusses a bit about the nature of Time, how to measure it (mentions days and nights), the use of conventional language for it and the fact that time is real.

    Book 11

    Discusses objects that float in the air, says "certain people conceive Earth circled by walls … and suppose that Earth is in the center of everything".

    Discusses where the sun rises and sets and distance; various models to interpret this. The commentators categorize this book as a polemic against the ancient astronomers who were using certain tools or machines (alluded to in this book) to evaluate the movements of celestial objects, and against Eudoxus' geocentric model. I looked this up and found this about Eudoxus of Cnidus:



    An astronomer named Eudoxus created the first model of a geocentric universe around 380 B.C. Eudoxus designed his model of the universe as a series of cosmic spheres containing the stars, the sun, and the moon all built around the Earth at its center. Unfortunately, as the Greeks continued to explore the motion of the sun, the moon, and the other planets, it became increasingly apparent that their geocentric models could not accurately nor easily predict the motion of the other planets.

    The next section of the 11th book is on what sustains Earth from below and seeks to explain its stability. Epicurus argued that densities below and above provide counter-balance to each other, to maintain the "appropriate analogical model" for the immobility of Earth. He said that the Earth was "equidistant to all the sides", and so it didn't fall in any direction because it had similar pressure from all sides.

    Now, since Epicurus believed the universe was infinite, we know that he would have rejected the Earth-centered model because an infinite model of cosmos would not have a center and all things would be relative to each other, there would be multiple centers. He is, in essence, explaining what an orbit is--an organized dance that acquires a certain balance of pushing and pulling and falling--without really having the word "orbit" for it.

    Here, from his use of "appropriate analogical model" which he presumably was trying to create, it is clear that he is using the Epicurean method of looking at things that can be observed and reasoning by analogy. This means that he appealed to how we can see that things of similar weight balance each other's forces, and he's applying that logic to the orbit of the Earth.

    Book 12


    I've noticed that E is addressing in each of these books phenomena that caused superstitious fear and panic in the ancients, or mythical explanations. Obviously, the orbit of the sun was a huge mystery and inspired the entire mythos of the Egyptian god Ra, while the phases of the moon inspired the Osiris mythical cycle. These were the common explanations in antiquity.

    I also surmise that some ancients, particularly those who rejected the myths and observed nature, would have observed that eclipses and phases of the moon apparently showed the shadow of the Earth against the moon, and would have reasoned that the Earth was round from the observation of its shadow against the moon. This is not mentioned in this book, but it would have been consistent with the Epicurean method to conclude the Earth was round.

    According to Philodemus, in book 12 (not extant portion) Epicurus said that humans had the idea of "certain imperishable natures" and this book appears to address theology also.

    Book 13

    Philodemus says that here, E addressed the "rapports of affinity, and also of hostility, that gods have with certain persons".

    So this seems to continue the conversations about gods in the previous book.

    "Please always remember my doctrines!" - Epicurus' last words

  • Book 10

    Discusses a bit about the nature of Time, how to measure it (mentions days and nights), the use of conventional language for it and the fact that time is real.

    A good example where it would be great to eventually compare the wording with precision. Time is "real"? And also time is an "incident of incidents / accidents of accidents" as in the letter to Herodotus? ( I think there is also a relevant quote in Lucretius):

    There is another thing which we must consider carefully. We must not investigate time as we do the other accidents which we investigate in a subject, namely, by referring them to the preconceptions envisaged in our minds; but we must take into account the plain fact itself, in virtue of which we speak of time as long or short, linking to it in intimate connection this attribute of duration. We need not adopt any fresh terms as preferable, but should employ the usual expressions about it. Nor need we predicate anything else of time, as if this something else contained the same essence as is contained in the proper meaning of the word “time” (for this also is done by some). We must chiefly reflect upon that to which we attach this peculiar character of time, and by which we measure it. No further proof is required: we have only to reflect that we attach the attribute of time to days and nights and their parts, and likewise to feelings of pleasure and pain and to neutral states, to states of movement and states of rest, conceiving a peculiar accident of these to be this very characteristic which we express by the word “time.”



    1 - I wonder about the term "neutral states" here.

    2 - I think it must be Lucretius where i recall the "accident of accidents" term. In either case I think it's interesting to observe that Epicurus can consider time an "accident" or "accident of accidents" and still also consider it to be real. This helps tune in the precise definition of "real." -- Things do not have to have an eternal unchanging existence to be "real."

  • Books 3-9 of On Nature are missing entirely. Les Epicuriens says that:

    Books 3-4 corresponds to paragraphs 49-53 L Herodotus

    (furthermore, Book 4 included E's theory of memory (where we would get a closer look into the Lucretian "neural pathways" passage and on neuroplasticity)

    Books 5-9 corresponds to paragraphs 54-73 L Herodotus

    So although we don't have these books, we can discuss the contents that were summarized in LHerodotus, and try to imagine what these books On Nature said, or their relevance to us today.

    "Please always remember my doctrines!" - Epicurus' last words