This piece contains four major ideas. They're mixed up with biographical detail and polemics so they can use a separate exposition:

A. Your words are not an encoding of your meaning

> [Y]our words are not an encoding of your meaning; they are a piece of evidence from which your meaning has to be inferred. [T]his can also be expressed by behavior, by gesture, and indeed by cultural symbols, where you convey that relevance will be achieved by orienting in a certain direction, by looking at certain things rather than others, by approaching them with a certain kind of expectation. There’s a continuum of cases between precise meanings that you can paraphrase and much vaguer effects

B. The paradox of cultural transmission

> [T]he paradox is that if you look at cultures, what you see is quite a bit of stability: The same words are being used more or less in the same sense for generation [...] the same tales are being told to children [...] the same recipes are being cooked [...] How can things stay so stable?

> [C]ommunication is not a replication system. When I communicate to you, you don’t get in your mind a copy of my meaning. You’ll transform it into something else. You extract from it what’s relevant to you.

> If you see a friend who has a great recipe for apple pie and you “imitate it,” you don’t really copy it. You look at it and you extract from it a way to do it your own way. There's a loss of information at every step, which is quite significant. [...] So how can you have this macro stability of cultural things with this micro failure to replicate?

> Fidelity [of copying] is not the only way to ensure stability. You can have stability [...] if the transformations that everybody produces at each step [...] converge, if you have what I can call a “cultural attractor”

C. Reason is an ability to share intuitions and justify ourselves in the eyes of others

> Why are reasons of any relevance to us? In our own individual thinking, reasons don’t matter very much. We trust ourselves. [...] You don’t need to look for a reason for what you intuitively believe. [...] But if we want to communicate to others what we believe and they don’t have the same intuitions, we may still share intuitions about reasons for our belief

> We use reason to justify ourselves. [... Others] have to think that the way we think and behave makes us reliable partners. The evidence they have is from what we do, which can be interpreted in a variety of ways. What we can do is provide reasons for our actions and our thoughts [...] to show that we had good reasons and can be trusted to have similarly good reasons in the future.

> It’s an ability to understand others, to justify ourselves in the eyes of others, to convince them of our ideas, to accept and to evaluate the justifications and arguments that others give and be convinced by them or not

>Rather than seeing as a paradox the fact that people can use reason to defend absurd ideas, as we see happen all the time, this is exactly part of what we assume is going to happen.

D. Science progresses by people using their reason to defend what they hit by luck

> It’s never the case for me, and rarely the case for anybody, that you gather so much evidence and data that somehow an idea emerges. [...] I think it’s mostly luck, when you hit on a good idea. Other people, just as bright and smart as you, have the bad luck of hitting on a bad idea. They invest a lot on the bad idea and they don’t get anywhere. If you have been lucky enough to hit on a good idea then, indeed, you’ll find confirming evidence, good evidence that will start explaining lots of things. But initially I think we’re groping in the dark.

> The kind of achievements that are often cited as the proof that reason is so superior, like scientific achievements, are [...] typically a product of social interaction over generations. They are social, cultural products, where many minds had to [...] progressively explore a lot of directions [...], not because some were more reasonable than others, but because some were luckier than others in what they hit. And then they used their reason to defend what they hit by luck.