On the whole, Aristotle did quite well at the task of discussing how matter comes to be, changes its state of being, and ceases to be. While the scientific resources available to a chemist or physicist today are much better than what was available in classical Athens during the 4th century B.C., Aristotle’s treatise On Generation and Corruption still constitutes an impressive investigation of the basic building blocks of existence.
I found out, after beginning On Generation and Corruption, that this work is a follow-up to Aristotle’s earlier treatise The Physics. Yeah, okay, so I should have read The Physics first: my bad. But I felt that the best thing I could do, having begun, was simply to soldier on with the work; and as I did so, I found Aristotle’s insights characteristically thorough and helpful.
The task that Aristotle sets for himself here is “to pick out the causes and definitions of generation and corruption common to all those things which come to be and perish in the course of nature” (p. 1). In other words, when something comes to be, is it a truly new coming-into-existence, of something that had no existence before; or is it an alteration or transformation from something else?
One of the examples that Aristotle brings up in that regard is that of eating and nutrition. We take in bread, meat or cheese, fruits or vegetables, water or wine, and those things undergo some sort of change, ceasing to be what they were and becoming part of who we are. A young person who eats plenty of healthy food may increase muscle mass as a result, thereby becoming a stronger person. Yet what exactly is going on there? Is it a process of generation (coming-to-be), or of corruption (ceasing-to-be), or of alteration? And when something grows, Aristotle asks, “how does [growth] differ from generation and alteration, and…how does each of the things that grow, grow, and everything that gets smaller, get smaller?” (p. 15)
Taking issue, as he often does, with earlier thinkers like the pre-Socratic philosopher Empedocles, Aristotle points out that there are circumstances under which “we see the same body, remaining continuous, at one time liquid and at another solid, and this happens to it without division or composition taking place…for it has become solid from being liquid without any change of order or position in its nature, nor does it have within it the hard and solid bodies, indivisible in their bulk, but it is at one time liquid in the same way throughout, and at another time hard or solid” (p. 32). In other words, there is alteration, but not any discernible generation or corruption.
If you have bad memories of a high school or college chemistry class where you had to memorize the entire Periodic Table of the Elements – all 118 of them, by the latest count – then you might find it comforting to know that in Aristotle’s time, “the elements are four in number”, and their properties can be summed up as follows: “[F]ire is hot and dry, air hot and wet (for air is something like steam), water cold and wet, and earth cold and dry” (p. 40). So much for having to memorize all those atomic weights and whatnot, right?
Aristotle’s ultimate conclusion, with regard to the question of whether things change in number or in form, is that it all depends upon whether the nature of what is to be changed is perishable or not. Accordingly, “water and air, for instance, come to be in a circle, and if there is a cloud it is bound to rain and if it rains there is bound also to be a cloud. Men and animals, on the other hand, do not return on themselves in such a way that the same one comes to be again…and it seems that this generation is in a straight line” (p. 59).
Thus spake Aristotle, back around 350 B.C. But what about now, in 2019 A.D.? What do people say about matter coming to be, and changing, and ceasing to be? Well, physicists nowadays believe that at the Big Bang, the very beginning of the universe, there was no matter – only light, in the form of photons. (“And God said, Let there be light: and there was light.”) The decay of those photons into particles and anti-particles eventually resulted in the generation of matter. Most particles and anti-particles cancelled one another out, destroyed each other, but enough particles survived to form all the matter in the universe. Getting more specific than that would involve talking about concepts like electroweak baryogenesis that, for now, are above my pay grade.
As for the continuance of matter, the Law of Conservation of Matter (or Conservation of Mass) holds that, in a closed system, the amount of mass or matter must remain constant; matter may be rearranged in space, or changed in form, but it will still be there.
And in terms of matter “ceasing-to-be,” the only circumstance under which that seems possible, under the constraints of the Law of Conservation of Matter, is when matter enters a collapsar or “black hole” and ceases to be part of the known universe. By this logic, matter approaches the singularity, the infinitely small and infinitely dense point of matter at the center of a black hole, and the known laws of physics cease to apply. But then other physicists, like Stephen Hawking, hold that perhaps that matter is still there, somewhere, and our instruments just can’t measure it yet.
Heady concepts, aren’t they? My mind is still reeling from reading this complex and challenging treatise from Aristotle. But it is great fun to think about how much Aristotle would have enjoyed accessing the modern equipment that physicists utilize to explore the universe. Imagine Aristotle looking at deep space through the Hubble Space Telescope, or reviewing results from the Large Hadron Collider in Switzerland, or just chatting with Stephen Hawking. How inspiring it is to see the conversation that Aristotle began continuing in this manner.