Nothing is harder to topple than a fact that supports a deeply held prejudice denied by its holder.

Traditional education focuses on teaching, not learning. It incorrectly assumes that for every ounce of teaching there is an ounce of learning by those who are taught. However, most of what we learn before, during, and after attending schools is learned without its being taught to us. A child learns such fundamental things as how to walk, talk, eat, dress, and so on without being taught these things. Adults learn most of what they use at work or at leisure while at work or leisure. Most of what is taught in classroom settings is forgotten, and much or what is remembered is irrelevant.

Common sense … has the very curious property of being more correct retrospectively than prospectively. It seems to me that one of the principal criteria to be applied to successful science is that its results are almost always obvious retrospectively; unfortunately, they seldom are prospectively. Common sense provides a kind of ultimate validation after science has completed its work; it seldom anticipates what science is going to discover.

No problem stays solved in a dynamic environment.

So much time is currently spent in worrying about the future that the present is allowed to go to hell.

Every problem interacts with other problems and is therefore part of a set of interrelated problems, a system of problems. I choose to call such a system a mess.

It is far better to do the right thing wrong than to do the wrong thing right.