There is a thought that stops thought. That is the only thought that ought to be stopped.

GK Chesterton, Orthodoxy

Why did I study philosophy? Many people have asked me this, usually accompanied with a follow-up question like, “What are you planning to do with that?” Usually when people ask me the latter, they do so assuming it has some connection with the former. They assume that the reason why I studied philosophy was in order to do something; but this is not true. If I’m being honest, the reason why I studied philosophy was because I sensed a problem that simply begged for my attention. How can we know anything at all?

The first philosopher that really touched me was René Descartes. In his Meditations on First Philosophy, he questioned how we could be certain of anything, and went as far as to say that for all we know, there might be a malicious demon deceiving us at every turn. The world we know, and our place in it, are all built on a shoddy foundation if we cannot disprove that hypothesis. Descartes had his own solution, of course; but I wasn’t convinced.

I went into my philosophical studies at university with this problem in mind, but just as I thought I had hit the bottom of the rabbit hole, I was surprised to find that I could keep going. I asked:

Why should my own reasoning have any validity?

Is my own reason capable of leading me to the truth at all?

How can I know that my reason itself is not a deception?

But of course, to reach a conclusion by the aid of reason which undermines reason is itself a contradiction. I had felt the cold aporia (a word the Greeks used to describe an impossibility, an uncertainty, or a puzzle) of philosophy. When left to its own devices—indeed, by being uncompromisingly rational—philosophy eats itself alive.

Chesterton himself (who I quoted earlier), when he described this problem, used this image of a serpent eating itself alive, called the Ouroboros. In it, what you see depicted is not merely an act of self-cannibalism, but is the very act of philosophy against which philosophy itself must be defended.