Talk is cheap.
To build fundamentally valuable skills, we need fundamentally reliable mechanisms of error correction.
And unfortunately, the world is full of misleading signals.
For instance: imagine I play you a song on the guitar (I don't know how to play the guitar).
Out of politeness, you might tell me I'm not that bad.
But if I asked you to buy a recording of my guitar songs for $20, I doubt you'd be so lenient.
Which brings us to the two forcing functions for truth: free markets (which teach us communication) and the laws of physics (which teach us to think from principles).
"Markets" can include any kind of voluntary transaction, not just monetary, and "physics" can include anything grounded in physical laws, not just rocket science.
The less diluted these are, the better.
Then, once we have a strong enough foundation, we can move on to the next step.