Ancient Greek famously made a distinction between 3 kinds of knowledge: doxa, episteme, and gnosis.

Doxa is basically what in English we might call hearsay. It’s the stuff you know because someone told you about it. If you know the Earth is round because you read it in a book, that’s doxa.

Episteme is what we most often mean by “knowledge” in English. It’s the stuff you know because you thought about it and reasoned it out. If you know the Earth is round because you measured shadows at different locations and did the math to prove that the only logical conclusion is that the Earth is round, that’s episteme.

Gnosis has no good equivalent in English, but the closest we come is when people talk about personal experience because gnosis is the stuff you know because you experienced it. If you know the Earth is round because you traveled all the way around it or observed it from space, that’s gnosis.

Often we elide these distinctions. Doxa of episteme is frequently thought of as episteme because if you read enough about how others gained episteme you may feel as though you have episteme yourself. This would be like hearing lots of people tell you how they worked out that the Earth is round and thinking that this gives you episteme rather than doxa. The mistake is understandable: as long as you only hear others talk about their episteme it’s easy to pattern match and think you have it too, but as soon as you try to explain your supposed episteme to someone else you will quickly discover if you only have doxa instead. The effect is so strong that experts in fields often express that they never really knew their subject until they had to teach it.

In the same way episteme is often mistaken for gnosis. At least since the time of Ptolemy people have had episteme of the spherical nature of the Earth, and since the 1970s most people have seen pictures showing that the Earth is round, but astronauts continue to experience gnosis of Earth’s roundness the first time they fly in space. It seems no matter how much epistemic reckoning we do or how accurate and precise our epistemic predictions are, we are still sometimes surprised to experience what we previously only believed.

But none of this is to say that gnosis is better than episteme or that episteme is better than doxa because each has value in different ways. Doxa is the only kind of knowledge that can be reliably and quickly shared, so we use it extensively in lieu of episteme or gnosis because both impose large costs on the knower to figure things out for themselves or cultivate experiences. Episteme is the only kind of knowledge that we can prove correct, so we often seek to replace doxa and gnosis with it when we want to be sure of ourselves. And gnosis is the only kind of knowledge available to non-sentient processes, so unless we wish to spend our days in disembodied deliberation we must at least develop gnosis of doxastic and epistemic knowledge to give the larger parts of our brains information to work with. So all three kinds of knowledge must be used together in our pursuit of understanding.

Unfortunately we tend to forget this and often privilege one kind of knowledge or discount another, resulting in several possible ways of failing to embrace the full richness of knowledge available to us. When a person downplays doxa relative to episteme and gnosis we might say they are too skeptical if we are generous and a sophist if we are not. When a person ignores episteme in favor of doxa and gnosis we might say they are unscientific or irrational. And when a person emphasizes doxa and episteme to the exclusion of gnosis we might call them an empiricist or, to be provocative, a rationalist.

In each case the cure is different. The sophist must learn compassion and empathy to be able to trust that producers of words, including their own past selves, may imbue them with some correlation to reality. The irrationalist must learn logic and parsimony so that they may accurately predict the world they will find themselves in. And the rationalist must learn humility enough to trust experience when facing what they don’t (or can’t) know through doxa and episteme. None is better than the other; all three are missing out on the fullness of what we can know.

It’s coincidental that ancient Greek chose to break knowledge into three kinds rather than two or four or five, but because it did we can think of doxa, episteme, and gnosis like the three legs of a stool. Each leg is necessary for the stool to stand, and if any one of them is too short or too long the stool will wobble. Pull one out and the stool will fall over. Only when all three are combined in equal measure do we get a study foundation to sit and think on.