I read Three Roads to Quantum Gravity (2001), by Lee Smolin, a theoretical physicist whose thoughtful style I’ve always appreciated. I don’t always agree with his ideas, though. This book is about Loop Quantum Gravity, in which Smolin has invested considerable effort, and that idea I’m utterly neutral on. It does seem to make more sense than string theory.
One notion I have a lot of trouble swallowing (like a cup of coffee with eight lumps of sugar) is the relational view. (As a philosophy, relationism. Al stayed home.) It’s a fundamental aspect of LQG.
But I (and apparently Kant agrees) think Leibniz was wrong.
Gottfried Leibniz (1646–1716) was a German polymath back when that actually meant something. The guy covered a lot of ground. Depending on who you talk to, either he, Newton, or both, discovered the calculus so many high school students hate.
Relevant here is that he’s also famous for holding relationist views about space and time. These in contrast to Newton’s view of absolute space and time. The relationist view makes relations the primary ontology.
We learned Newton was wrong about space and time when Einstein showed that spacetime is a unified fabric, and space, time, simultaneity, and the idea of “now” are strictly relative and local. Newton being wrong about this doesn’t necessarily mean Leibniz was right, though.
Einstein showed that space and time are relative, which is not the same thing as relational. Special Relativity is a theory of objects. (One could call the view-dependent nature of relativity a relation between perspective and view, but it’s a secondary property, as I’ll explain below.)
I’ve seen references to Immanuel Kant (1724–1804) debunking both Leibniz and Newton on their time and space views. It’s one of those things on my long list of things to check out if I ever get around to it. Kant is heavy going (most serious philosophers are), so I’ve put it off. Math and quantum mechanics are eating up my CPU cycles these days.
Kant did feel that time (foremost) and space were our most basic intuitions, and that they framed our every perception and thought. That only means we’re “wired” to comprehend reality in their context. It doesn’t require that time and/or space are fundamental. (I’ve always found it suggestive and compelling, though.)
Smolin agrees with Leibniz and promotes Loop Quantum Gravity as a relationist physical theory.
In fact, that’s related to the theory’s biggest sales point, that it’s a background independent theory. Like General Relativity, it creates the background. Space, and everything else, emerge from these relationships.
Except time. Smolin doesn’t touch on time much in Three Roads, but I just started his 2013 book, Time Reborn, and there he says plenty in just the Preface:
“More to the point, I no longer believe that time is unreal. In fact, I have swung to the opposite view: Not only is time real, but nothing we know or experience gets closer to the heart of nature than the reality of time.”
I laughed out loud when I read it. I’ve been saying the same thing forever (see these posts). Here it’s not that I agree with the expert in the book, but that the expert, after long consideration, now agrees with me. Ha!
But back to LQG and relationism.
The loops in Loop Quantum Gravity are connections between minimum-sized volumes of… well, not volumes of space, because the whole point is this theory defines space, so… volumes of volume, I guess.
Smolin says the connections, the relations, are the main ontology, but his own text contradicts that. Like, constantly. Every example he gives of relations has objects that anchor those relations.
(It reminds me of how when strict determinists say free will doesn’t exist they can’t avoid constantly using words like “choose”. Some say this is because language is inadequate. Perhaps, but it can also, I think, speak to incoherency in the idea.)
Maybe it’s a limit on my part, but I’m not sympathetic to relational theories . They always seem to imply objects for the relations to be between. I’m not sure relations as the only, or even primary, ontology is a coherent notion. I think relations are always secondary and contingent on (at least) two objects.
Look at it this way: Does the idea of a relation between nothing make sense? Just a relation as a primary ontological object.
The general notion of a relation has a certain Platonic weight, but notice what the notion entails: “A relation is a set of properties describing a link between…” Oops.
A link between what? The definition can’t continue until we supply objects for a relation to be between.
A naked relation doesn’t seem a complete notion. It needs something to complete it. Here’s a simple example:
Without an x and a y, the relation is incomplete.
On the other hand, the idea of two objects with no relation makes perfect sense. Ontologies begin with things. Once you have things, you can have relations between them.
Now that makes sense. It’s not true, but it makes sense. It can be parsed, understood, and processed.
Bottom line, I just don’t get relationism. To me it’s cart before horse.
As an aside, Smolin suggests that string theory might be a background dependent approximation where LQG is the underlying theory providing that background. According to him, the strings would ride on the spin network (the “loops” in LQG).
He also compares string theory with the simplified Newtonian view (which was also background dependent). That Newtonian view was necessary for progress in understanding motion. Einstein later updated it, but Newton still works great for lots of stuff. We sent New Horizons to Pluto with it.
Stay looped, my friends! Go forth and spread beauty and light.