Epicurus was an Athenian, around shortly after Aristotle (341-270 BC). His biographer says that he turned to philosophy because his schoolteachers could not satisfactorily interpret the ÎChasm/ Voidâ in Hesiod for him. He was extremely kind to everyone. He was content to eat only water and bread; said in a letter ãSend me a little pot of cheese so that I may indulge in extravagance when I wish.ä And this is the same person who taught that Îpleasure is the goalâ (hence our ÎEpicureanâ = hedonist). He was a voluminous writer, but we only have three summary letters, and some fragments and maxims.
Lucretius came many years after Epicurus (died 55 BC); he was a Roman during a time when the Roman Republic was politically powerful, a contemporary of Cicero. He wrote a poem called "On the Nature of Things" (De Rerum Natura). This is a defense of Epicurusâ natural philosophy, but it is written at a more popular, mass-appeal level, and is encyclopedic in scope. (Much of Roman writing on natural philosophy was aimed at a popular audience.)
Epicurus writes ãI recommend constant activity in the study of nature; and with this activity more than any other I bring calm or peace to my lifeä (LH). In short: by stressing the explanatory power of the idea that all that exists is atoms in the void, we can overcome our fear of death. The aim of philosophy is happiness. The way to achieve happiness was to eliminate fear of the unknown and supernatural. Natural philosophy (i.e. science) is subordinated to ethics.
This is Parmenides' familiar principle. But Epicurus gives new arguments for this old thesis, using a reductio strategy. Suppose for the sake of contradiction that x could come to be out of what is not-x. Then birds could come to be out of rocks, sunlight, humans, and fish (since all of these are not-birds). (GF: this seems very Aristotelian to me; for how do fish-atoms Îknowâ that they are fish atoms and know how to arrange themselves in the developing offspring in just the right way? If some atoms are goal-directed in this way (acorn-atoms will always progress to eventually be atoms in an oak tree), then it seems like nature is teleological, as Aristotle argued in Physics II.8.)
1. ãThat bodies exist is universally witnessed by sensation itself.ä
2. If void did not exist, then the bodies would have no place to move. But we see bodies moving (and, contra Parmenides, this sensation reveals the truth). Thus void exists.
3. Nothing else exists, because ãbeyond these nothing can be thought of, either by imagination or by analogy with what is imagined, as completely substantial things and not as the things we call accidents and properties of theseä (27-8). [GF: Whatâs the criterion for Îcompletely substantialâ??? Isnât he begging the question here?] Lucretiusâ explanation (28): ãFor whatever will exist will have to be in itself something with extension· and if it is intangible, and hence unable to prevent anything from moving through it at any point, it will undoubtedly be the emptiness we call void.ä The definition of Îbodyâ is Îthat which offers resistance to touchâ and the definition of Îvoidâ is Îthat which does NOT offer resistance to touch (p. 35). Everything else that exists does not exist per se (as separable, independently). These qualities exist at the phenomenal level, not at the atomic level.
~ We see in this quotation Epicurusâ epistemology (theory of knowledge) as well. Sensation is to be the judge of any claim about the visible, tangible world, and reason is to be the judge of claims concerning the Înon-evident,â i.e., the invisible and intangible. We get examples of each kind of judgment here. Bodies exist because our senses say they do. And the existence of void or place is justified by reason in tandem with the perception that motion takes place, since we cannot see or touch the void (void is true, total emptiness, a Îvacuumâ in modern language, so air is not void).
1. Bodies that appear solid are actually porous (e.g. water falls through cave walls).
2. Objects can be the same size and shape but weigh different amounts; different relative densities entails that one must have more space in it than the other, heavier one.
Like all the philosophers we have read so far, Epicurus has definite views about what is ontologically basic (Îper se substancesâ) and what is derivative. The only Îper se substancesâ are atoms and void (though void is a strange kind of substance; it is nothing). Now, the per se substances have certain Îfixedâ or permanentâ attributes (attributes that cannot be removed without destroying the substance, e.g., fire is hot): all body is touchable, has some shape, has some size, and has some weight. All other attributes of body are accidental (e.g., being part of a book or a table are accidental (coincidental, inessential) attributes of the atoms that comprise the book or table).
Premise 1. Full body and void cannot occupy the same place simultaneously.
Premise 2. An object cannot be cut unless it has some void in it, for otherwise, there would be no place for the blade (or whatever) to go.
P3. But an object would not be an object at all unless there is at least SOME full body in it. Therefore, there must be some part (however small) of every object that is full body. Then, by P2, we have that there must be some small part of every object that is uncuttable, that is, Îatomic.â
~ P2 yields the conclusion that an atom and its shape are indestructible (you cannot cut or pound them into another shape, or out of existence). Since atomsâ shapes are unchanging, this can provide an explanation of the overwhelming regularity of complex natural processes, especially biological ones. Thus we have a purely material, geometrical explanation of the phenomena that led Aristotle to posit the existence (and importance) of form and final cause. We have a tentative solution to the worry expressed at the beginning, in which Epicurus sounded fairly Aristotelian in his justification of Parmenidean principles. (This Epicurean idea should be read as an alternative to Aristotle's Physics II.8.)
The doctrine of Îminimal partsâ is truly bizarre. It is an attempt to cope with Zenoâs paradoxes of motion. It says more than Îyou cannot cut a body into infinitely many parts.â Rather, it goes further and claims that a body just does not have infinitely many parts.
First argument: If there are an infinite number of magnitudes (ãbitsä) in a body or place, then motion of that body to another place will be impossible. Why? The body would have to travel through an infinite number of magnitudes in a finite time. But sense-experience tells us unequivocally that motion does in fact occur. Therefore there are not an infinite number of magnitudes in a given body or place.
Second argument: If there are an infinite number of parts in a finite magnitude, then when we added up all these component parts, we would get an infinitely large magnitude as our sum. But we assumed the magnitude was finite. Therefore, there cannot be an infinite number of segment-parts. So there are minimum magnitudes that compose any magnitude.
There are an infinite number of atoms, space extends out infinitely in all directions (contra Aristotle and Plato), and the universe is eternal (contra Plato, pro Aristotle). There are unimaginably many shapes/ kinds of atoms, but the number of different shapes is finite (otherwise there would be large, visible atoms).
This can be seen as a criticism of Plato's Timaeus
1. The workings of the world are not all caused by the godsâ wills and desires. Why?
(a) The world is infinite, and there are an infinite number of bodies; how could a single entity rule the infinite? P.58D: ãWho is capable of ruling the totality of the measureless,·? Who could turn all those heavens at the same time?ä
Especially when the gods are supposed to enjoy a state of ãtranquil peace, leading their life of calm serenityä (p.58D). (See also p. 61, where the god who spins the cosmos is described as ãextremely overworked.ä)
(b) Gods would not create the world for the sake of humans (p.59F): ãwhat profit could imperishable and blessed beings gain from our gratitude, to induce them to take on any task for our sake? What novelty could have tempted hitherto tranquil beings, at so late a stage, to desire a change in their earlier lifestyle?ä Do not worry about the gods, because if the gods are really great, then they do not need our prayers and sacrifices.
(c) What would cause the gods to begin creating at one moment, rather than another?: ãA question for both of you is why the world-builders suddenly appeared on the scene, after sleeping for countless centuriesä (p.61G). This argument originally appeared in Parmenidesâ poem.
(d) (p. 60) The world is a terrible place for humans, so it cannot be ãa divine gift to us.ä
(e) (p.61top) The world must be eternal, so it does not have a craftsman. And nature teaches us that anything with a beginning has an end.
2. The world, and the things in it, are not created to satisfy a purpose. Items do not come into existence to fulfill a function. Why? Sight did not exist before eyes, therefore sight cannot have caused the eye to exist (I guess Lucretius is relying on the principle that a cause must precede its effect). We are mistaken, and think that the world and its parts come into existence, because we confuse artifacts and human creations with natural objects and parts.