This is an excerpt from The Cosmic Machine: The Science That Runs Our Universe and the Story Behind It

By Scott Bembenek, PhD

The ancient Greek philosophers played a significant role in shaping the initial thoughts about atoms. Several of the ancient philosophers pondered and developed a theory of matter, with one even imagining the existence of a fundamental building block that made up not only all living and nonliving things, but the supernatural as well. Their thoughts were speculative and philosophical, rather than scientific in nature. And while they attempted to touch on the nature of matter and its composition, their real goal was to address something of profound concern to the ancient Greeks: the nature of permanency and change. Unfortunately, these “theories” of matter were rather short-lived. Although there was some revival during the Middle Ages and the Renaissance, they never gained any real momentum until the seventeenth century.

Permanency and Change

The Greek philosopher Heraclitus (c. 540 BC–c. 475 BC) was a native of the Greek city Ephesus on the coast of Asia Minor, or present-day Turkey. What we know of Heraclitus’ works mainly comes from surviving fragments from Plato and Aristotle, where it was quoted for the sake of rebuttal, and from Diogenes Laërtius (c. third century), a biographer of Greek philosophers, who also gives us insight into his life in general.

Heraclitus, as a pessimist, had mostly contempt for mankind. He ridiculed Homer, who he claimed should have been turned out and whipped, and had nothing but scorn for several of the intellects of the time such as Pythagoras (c. 560 BC–c. 480 BC) and Xenophanes (c. 570 BC–c. 480 BC). Even of his fellow citizens of Ephesus he said, “[They] would do well to hang themselves, every grown man of them, and leave the city to [children].”

Heraclitus saw everything in the universe as being in a constant state of change, where nothing remained the same for even the slightest moment in time (he even said the Sun is new every day). This doctrine of flux means, for example, that one would never be able to touch the same object twice; you could touch an object once, but by the time you touch it again it would have already changed its state, according to Heraclitus. But the idea that everything is changing is at odds with our everyday senses, which tells us that some things do seem to maintain a sort of permanency.

Heraclitus addresses this “appearance” of permanency with the following example: while a river gives the impression of being something permanent, the water is constantly flowing, and as such the river is really in a constant state of change. It’s interesting to note that Heraclitus’ theory of constant change isn’t far from reality. Imagine an object such as a glass of water sitting on your kitchen counter. Suppose that throughout the course of the day you notice this glass of water several times over, and, of course, never is there any noticeable change in its appearance. For the most part, from a macroscopic perspective, the glass of water is the same. It had the same temperature, volume, and number of water molecules each time you looked at it.

However, from a microscopic perspective things were constantly changing. The molecules of water in the glass have been and will continue to be in constant motion. To be sure, Heraclitus had no knowledge of atoms and molecules, and therefore this specific example would have never occurred to him. Although Heraclitus didn’t believe in atoms, he did believe in fundamental building blocks of matter, or principal “elements.”

Heraclitus believed in three principal elements: earth, air, and fire. Among these, he chose fire as the “primary element.” His choice of fire as the primary element is in the same spirit as the aforementioned river. When one views fire, it’s easy to imagine it as unchanging, as the flame burns without any significant signs of change. However, in reality it changes by virtue of its constant consumption of the very fuel needed to keep that same flame going. Thus, fire was the source of all other matter, according to Heraclitus: “All things are an exchange for Fire, and Fire for all things ….” Moreover, while everything in the universe is in a state of constant change, the universe itself is eternal. He says, “was ever, is now, and ever shall be an ever-living Fire ….” While Heraclitus promoted the universe as being in a constant state of change, Parmenides was claiming the exact opposite.

The Greek philosopher Parmenides (c. 515 BC–c. 450 BC) was born into a wealthy and illustrious family in the Greek city Elea, on the southern coast of present-day Italy. He was the founder of the School of Elea, and his most prominent pupil was Zeno (c. 490 BC–c. 425 BC), whose works may have been the first to use the method of reductio ad absurdum. Parmenides had a strong influence on other philosophers, particularly Plato, who spoke highly of him and even wrote a dialogue named after him. Indeed, Plato’s “Theory of Ideas” may have been influenced by the ideas of Parmenides. All that survives of Parmenides’ work is the poem On Nature, which sets forth his doctrine.

In the first part of the poem, “The Way of Truth,” Parmenides tell us the universe is changeless, and what we think is change is merely an illusion. Part of the disparity between Heraclitus and Parmenides arises from the fact that Heraclitus believed unconditionally in one’s sense, whereas Parmenides insisted that our senses serve only to deceive us. For Parmenides, simply thinking of something gave it an existence: “Only that can really exist which can also be thought.”

The essence of Parmenides’ argument against change goes like this: every time you think of or speak of something, that thought or word must pertain to something that actually exists. In other words, in order for a thought to be conceivable and language to be sensible, they both require objects outside themselves. Now, since at any given moment you can think of or speak of anything, everything must exist at all times. Therefore, there can’t be change since change requires something to either come into existence or pass from existence.

So, according to Parmenides if something exists, it exists for all time, and therefore it has no beginning or end, which makes it infinite in a sense. Moreover, arguing against the possibility of more than one thing being infinite (infinity is a unique state), Parmenides makes his second big conclusion: everything that exists is unified under “The One.” Parmenides was a strict monist.

OK, so if you’re having trouble following some of the logic of Parmenides, you’re not alone. His original writings are hard to follow, and we are indebted to others for clarification. Besides, today we agree that Parmenides’ logic was unsound. The take-home message is that Parmenides, unlike Heraclitus, believed change was merely an illusion brought into existence only as a result of our deceptive senses; the real state of the universe is a state of permanency. In addition, he believed that the universe was unified under a single existence rather than several individual ones. Finally, take a moment to realize that Parmenides’ insistence on our senses being nothing but tools of deception implies the impossibility of ever realizing meaningful experimental science.

These main points of Parmenides, along with Heraclitus’ insistence that the actual state of the universe was one of constant change, had an enormous impact on succeeding philosophers. This is especially true of those who developed theories of matter. The main goal of these ancient theorists was to unify, in some sort of way, the disparate doctrines of Parmenides and Heraclitus, rather than to construct a complete physical theory of matter. Nonetheless, out of their initial efforts we find the beginnings of atomic theory, with one in particular bearing a striking resemblance to modern atomic theory.

Dr. Scott Bembenek is a principal scientist in the Computer-Aided Drug Discovery group at Johnson & Johnson Pharmaceutical Research & Development in San Diego. He is also the author of The Cosmic Machine: The Science That Runs Our Universe and the Story Behind It. To learn more about Dr. Bembenek and his work, visit http://scottbembenek.com and connect with him on Twitter

IMAGE CREDIT: Wellcome Library

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