Why does Descartes think that atoms and vacua are impossible?

Descartes’ Rejection of Atoms and Vacua: A Matter of Metaphysics (Humanized)

René Descartes, that philosophical rockstar from the 17th century, wasn’t just pondering “I think, therefore I am.” He also had some pretty strong opinions about physics, specifically, why he thought atoms and empty space – vacua – were complete impossibilities. Now, this wasn’t just a scientific squabble for him; it all boiled down to his core beliefs about what stuff is actually made of and the very nature of space itself. So, to get why he dismissed these ideas, we need to dive into his rather unique view of the physical world.

For Descartes, the defining characteristic of matter was simply that it takes up space. Think length, width, and depth – that’s it. He believed that extension, as he called it, was the one thing we could really, truly understand about matter. Seems simple enough, right? But this idea had some seriously far-reaching consequences.

Here’s where it gets interesting. Descartes thought a vacuum, a space with absolutely nothing in it, was just plain illogical. Why? Because if matter is extension, then you can’t have extension without matter, and vice versa. It’s like saying you can have a smile without a face – doesn’t quite work, does it? For Descartes, space itself is a kind of matter. So, a space devoid of matter would be a space without any extension, which, in his mind, was a total contradiction. He basically echoed the old Aristotelian idea that all space is filled with something – a plenum, they called it. So, his rejection of the vacuum wasn’t based on looking through a telescope or anything; it was a purely philosophical argument about what existence even means.

And what about atoms, those tiny, indivisible building blocks of everything? Descartes wasn’t a fan of those either. His main beef was with the idea that matter couldn’t be divided. See, if matter is just extension, then any piece of matter, no matter how small, has to have length, width, and depth. And if it has those things, then you can, at least in theory, cut it in half!

He argued that even if God created particles “indivisible by any of his creatures,” God himself would still be able to divide them. It all boils down to this: the idea of something that takes up space but can’t be divided just didn’t make sense to him.

So, instead of atoms floating around in empty space, Descartes envisioned a universe jam-packed with a continuous, almost ethereal substance – his plenum. This stuff wasn’t all the same; it was more like a cosmic soup of particles in constant motion. He even categorized it into elements: fire, air, and earth, with fire being the tiniest, fastest bits and earth being the big, slow ones.

To explain how planets move, Descartes came up with these swirling masses of subtle matter called vortices. Imagine giant whirlpools carrying planets around the sun. It was his attempt to explain how the cosmos worked without any empty space. He figured the sun and stars were made of fire, and the heavens were mostly air with a dash of fire thrown in for good measure.

Now, while Descartes’s specific ideas about vortices and elements didn’t exactly stand the test of time (Newton eventually came along and shook things up), his emphasis on explaining the world through mechanics and math was a huge deal. His laws of motion, for example, were a major contribution, even influencing Newton himself.

In the end, even though modern physics has moved way beyond Descartes’s picture of the universe, his reasons for rejecting atoms and vacua are still fascinating. They show us a philosopher deeply committed to a particular view of reality, where space and matter are inseparable, and where the possibility of division is built into the very fabric of existence. It’s a reminder that even the most brilliant minds can be shaped by their fundamental beliefs about the world.