C. Ancient Philosophy: 2nd Student Essay
'All that exists are atoms and the void.' What is an atom? What is the void?
Among all those that tried to reconcile the sensory experience with Parmenidean metaphysics, the most successful were Leucippus and Democritus, the founders of atomic theory.
They maintained that (Kirk, Raven and Schofield The Presocratic Philosophers para 555) the elements are two, the whole and the void, calling them being and non-being. Being is full and compact, non-being is void and thin. In Aristotle's words,
Democritus believes that the nature of the eternal things is small substances [OUSIAI] unlimited in multitude. As a place for these he hypothesises something else, unlimited in size, and he calls the place by the names 'void', 'nothing' [OUDEN], and 'unlimited' [or, infinite'] and he calls each of the substances 'thing' [DEN] and 'compact' and 'what is'.
This substances are so small that escape from our senses, but they have every kind of form, shape and difference in magnitude. Aristotle adds, 'he composes from them, exactly as if from elements, by congregating them, the bodies that are perceivable with vision and the rest of the senses' (KRS para 556).
In this way, all qualitative differences of the objects (which are complexes of atoms) we experience are deduced to quantitative differences as well as differences in position and arrangement.
Atomists followed, to some degree, Eleatic doctrines: They call 'genuine' the knowledge that we obtain intellectually, and 'illegitimate' the knowledge that we derive from our senses. So they agree that senses are not safe advisors for the deepest nature of reality, but still they accept that senses inform us truly that many things do exist and that genesis, decay and motion take place. What actually the atomists say, is that sense experience is not adequate for knowledge; it needs to be interpreted by our reasoning (contrary to Eleatics which gave no value at all to sensory data).
Furthermore, Parmenides' disciple Melissus had admitted (KRS para 537) that 'if many things existed, they would had to be exactly as the one', while Zeno had 'proved' that if being is divisible, absurd consequences arise. The atomists adopted both ideas. They said that (KRS para 557) the first principles of beings are infinite in number and they believed that those are indivisible ('atoms') and unaffected, for they are compact, as well that they do not have any void inside; because division is due to the void that exists within bodies (therefore they consider atoms indivisible not intellectually but naturally). The differences among atoms are three: regarding shape, arrangement and position.
So, the atomists agreed with the basic Parmenidean doctrines: that being can not be derived from non-being and the opposite, as well as that being is whole, unalterable, unborn and indestructible. But now, there is not only one being but many, separated by void.
The atomists' main ingenuity consists exactly in the admission that void, viz. non-being, does exist. According to them, 'There is no more reason for the thing to be than the nothing' (KRS p. 411 n. 2).
So they readmitted the notion of non-being in the form of the void, within which atoms move freely, just because there is not any specific reason why the void should not exist. The re-introduction of non-being still remains the main problem for the coherence of the theory. Of course here being is not derived from non-being nor does it return to non-being, and therefore vanishes Parmenides' main reason for rejecting the existence of non-being. The problem which remains is the logical content of the notion non-being (=what does not exist) itself. Perhaps they identify non-being unintentionally with void, for even if they assert that there exist two material principles, those two principles are not complementary, as the only role of non-being is actually to give space for atoms to move through (while Parmenides, for instance, had used two really complementary principles by using light and dark in his 'Way of Opinion').
In Aristotle's approach, void is exactly the same as 'space'. For our contemporary scholars, however, the original doctrine is that void exists only to the extent that something occupies a position, and thus it is just the negation of substance. Therefore space, we can assume, has an independent existence, apart from void and atoms. Many centuries later, Kant would maintain that space and time is the necessary framework through which human mind can conceptualise the world of appearances. But for the atomists, we have to accept that space is just an empirical feature of reality, introduced in an otherwise metaphysical theory.
We can find the same mixture of empirical and metaphysical features, when we examine the characteristics of beings, that is of atoms. Actually, according to the atomists' description, atoms look a lot like small objects of every day experience, with various shapes and various weights (we must accept that all of them have the greater possible density, since they all consist of being alone), but with no other features, like colour, smell etc.
At any rate, Atomists are the precursors of the prevailing contemporary way of explaining reality, especially in the natural sciences: That is that all our sensory data is explained by the existence of tiny particles with few primary features (like shape, position, direction, mass) which are the only beings that really 'exist' (in our days of course we inquire separately the attributes of the space-time framework within which all motion takes place). Today's science can now 'prove' the existence of its theoretic primary entities through experiment, while ancient Atomism was a metaphysical theory, that is a product of pure logic. Still, in modern physics we can see also the same ancient problem: how can we describe something that has nothing to do with every day experience, but still we must call it a particle? This is perhaps the root of the dualism particle-wave that the scientists have introduced to describe the behaviour of what they call 'particles'.