It's a lot easier to see, at least in some cases, what the long-term limits of the possible will be, because they depend on natural law. But it's much harder to see just what path we will follow in heading toward those limits.

Likewise nanotechnology will, once it gets under way, depend on the tools we have then and our ability to use them, and not on the steps that got us there.

In a sense, artificial intelligence will be the ultimate tool because it will help us build all possible tools.

After realizing that we would eventually be able to build molecular machines that could arrange atoms to form virtually any pattern that we wanted, I saw that an awful lot of consequences followed from that.

The basic parts, the start-up molecules, can be supplied in abundance and don't have to be made by some elaborate process. That immediately makes things simpler.

Scientists study physical things, then describe them; engineers describe physical things, then build them.

Nature draws no line between living and nonliving.