Eliezer Yudkowsky

The strength of a theory is not what it allows, but what it prohibits; if you can invent an equally persuasive explanation for any outcome, you have zero knowledge.

Your strength as a rationalist is your ability to be more confused by fiction than by reality. If you are equally good at explaining any outcome, you have zero knowledge.

If our extinction proceeds slowly enough to allow a moment of horrified realization, the doers of the deed will likely be quite taken aback on realizing that they have actually destroyed the world. Therefore I suggest that if the Earth is destroyed, it will probably be by mistake.

In our skulls, we carry around 3 pounds of slimy, wet, greyish tissue, corrugated like crumpled toilet paper. You wouldn't think, to look at the unappetizing lump, that it was some of the most powerful stuff in the known universe.

[...] intelligent people only have a certain amount of time (measured in subjective time spent thinking about religion) to become atheists. After a certain point, if you're smart, have spent time thinking about and defending your religion, and still haven't escaped the grip of Dark Side Epistemology, the inside of your mind ends up as an Escher painting.

The obvious choice isn't always the best choice, but sometimes, by golly, it is. I don't stop looking as soon I find an obvious answer, but if I go on looking, and the obvious-seeming answer still seems obvious, I don't feel guilty about keeping it.

When something is universal enough in our everyday lives, we take it for granted to the point of forgetting it exists.

To be clever in argument is not rationality but rationalization.

Since the rise of Homo sapiens, human beings have been the smartest minds around. But very shortly - on a historical scale, that is - we can expect technology to break the upper bound on intelligence that has held for the last few tens of thousands of years.

If you are equally good at explaining any outcome, you have zero knowledge.

I ask the fundamental question of rationality: Why do you believe what you believe? What do you think you know and how do you think you know it?

Science has heroes, but no gods. The great Names are not our superiors, or even our rivals, they are passed milestones on our road; and the most important milestone is the hero yet to come.

There are no surprising facts, only models that are surprised by facts; and if a model is surprised by the facts, it is no credit to that model.

To confess your fallibility and then do nothing about it is not humble; it is boasting of your modesty.

What people really believe doesn't feel like a BELIEF, it feels like the way the world IS.

Trying and getting hurt can't possibly be worse for you than being... stuck.

There is no justice in the laws of nature, no term for fairness in the equations of motion. The Universe is neither evil, nor good, it simply does not care. The stars don't care, or the Sun, or the sky. But they don't have to! WE care! There IS light in the world, and it is US!

Why does any kind of cynicism appeal to people? Because it seems like a mark of maturity, of sophistication, like you’ve seen everything and know better. Or because putting something down feels like pushing yourself up.