I try not to invent things that people don't need.

The greatest invention in the world is the mind of a child.

To invent, you need a good imagination and a pile of junk.

Negative results are just what I want. They're just as valuable to me as positive results. I can never find the thing that does the job best until I find the ones that don't.

Anything that won't sell, I don't want to invent. Its sale is proof of utility, and utility is success.

Writing ... is the great invention of the world.