What are the limits of knowledge?

 This was the Question of the Month in Philosophy Now (Issue 157, August/September 2023) and 11 answers were published in Issue 159, December 2023/January 2024, including mine, which I now post complete with minor edits.

 

Some people think that language determines the limits of knowledge, yet it merely describes what we know rather than limits it, and humans have always had the facility to create new language to depict new knowledge.

There are many types of knowledge, but I’m going to restrict myself to knowledge of the natural world. The ancient Greeks were possibly the first to intuit that the natural world had its own code. The Pythagoreans appreciated that musical pitch had a mathematical relationship, and that some geometrical figures contained numerical ratios. They made the giant conceptual leap that this could possibly be a key to understanding the Cosmos itself.

Jump forward two millennia, and their insight has borne more fruit than they could possibly have imagined. Richard Feynman made the following observation about mathematics in The Character of Physical Law: “Physicists cannot make a conversation in any other language. If you want to learn about nature, to appreciate nature, it is necessary to understand the language that she speaks in. She offers her information only in one form.”

Meanwhile, the twentieth century logician Kurt Gödel proved that in any self-consistent, axiom-based, formal mathematical system, there will always be mathematical truths that can’t be proved true using that system. However, they potentially can be proved if one expands the axioms of the system. This infers that there is no limit to mathematical truths.

Alonso Church’s ‘paradox of unknowability’ states, “unless you know it all, there will always be truths that are by their very nature unknowable.” This applies to the physical universe itself. Specifically, since the vast majority of the Universe is unobservable, and possibly infinite in extent, most of it will remain forever unknowable. Given that the limits of knowledge are either infinite or unknowable in both the mathematical and physical worlds, then those limits are like a horizon that retreats as we advance towards it.