I've cut & pasted selected ideas from his essay . If you have time, it's certainly worth reading his original post.
"Once you start to examine the question, it's surprising how much different fields' ideas of beauty have in common. The same principles of good design crop up again and again.
Good design is simple. When you're forced to be simple, you're forced to face the real problem. When you can't deliver ornament, you have to deliver substance.
Good design is timeless. Aiming at timelessness is a way to make yourself find the best answer. Aiming at timelessness is also a way to evade the grip of fashion.
Good design solves the right problem.
Good design is suggestive.
Good design is often slightly funny. Good design may not have to be funny, but it's hard to imagine something that could be called humorless also being good design.
Good design is hard. If you look at the people who've done great work, one thing they all seem to have in common is that they worked very hard. If you're not working hard, you're probably wasting your time.
Good design looks easy. Like great athletes, great designers make it look easy. Mostly this is an illusion. The easy, conversational tone of good writing comes only on the eighth rewrite.
Good design uses symmetry.
Good design resembles nature. It's not so much that resembling nature is intrinsically good as that nature has had a long time to work on the problem.
Good design is redesign. It's rare to get things right the first time. Mistakes are natural. Instead of treating them as disasters, make them easy to acknowledge and easy to fix.
Good design can copy. [The greatest masters] just want to get the right answer, and if part of the right answer has already been discovered by someone else, that's no reason not to use it. They're confident enough to take from anyone without feeling that their own vision will be lost in the process.
Good design is often strange.
Good design happens in chunks. Nothing is more powerful than a community of talented people working on related problems.
Good design is often daring.
"Great work usually seems to happen because someone sees something and thinks, I could do better than that."
Excerpts from "Taste for Makers" by Paul Graham February 2002
Thanks to Alyce Brady for suggesting his essay.