When facing a scientific theory they disagree with, scientists are supposed to try to disprove it by scientific methods. Molecular manufacturing includes a substantial, well-grounded, carefully argued, conservative body of work. So why do scientists treat it as though it were pseudoscience, deserving only political attack? And how should they be approaching it instead? To answer this, we have to consider the gap between science and engineering.

Scientists do experiments and develop theories about how the world works. Engineers apply the most reliable of those theories to get predictable results. Scientists cannot make reliable pronouncements about the complex "real world" unless their theory has been field-tested by engineering. But once a theory is solid enough to use in engineering, science has very little of interest to say about it. In fact, the two practices are so different that it's not obvious how they can communicate at all. How can ideas cross the gap from untested theory to trustworthy formula?

In Appendix A of Nanosystems*, Eric Drexler describes an activity he calls "theoretical applied science" or "exploratory engineering". This is the bridge between science and engineering. In theoretical applied science, one takes the best available results of science, applies them to real-world problems, and makes plans that should hopefully work as desired. If done with enough care, these plans may inspire engineers (who must of course be cautious and conservative) to try them for the first time.

The bulk of Appendix A discusses ways that theoretical applied science can be practiced so as to give useful and reliable results, despite the inability to confirm its results by experiment:

For example, all classes of device that would violate the second law of thermodynamics can immediately be rejected. A more stringent rule, adopted in the present work, rejects propositions if they are inadequately substantiated, for example, rejecting all devices that would require materials stronger than those known or described by accepted physical models. By adopting these rules for falsification and rejection, work in theoretical applied science can be grounded in our best scientific understanding of the physical world.

Drexler presents theoretical applied science as a way of studying things we can't build yet. In the last section, he ascribes to it a very limited aim: "to describe lower bounds to the performance achievable with physically possible classes of devices." And a limited role: "In an ideal world, theoretical applied science would consume only a tiny fraction of the effort devoted to pure theoretical science, to experimentation, or to engineering." But here I think he's being too modest. Theoretical applied science is really the only rigorous way for the products of science to escape back to the real world by inspiring and instructing engineers.

We might draw a useful analogy: exploratory engineers are to scientists as editors are to writers. Scientists and writers are creative. Whatever they produce is interesting, even when it's wrong. They live in their own world, which touches the real world exactly where and when they choose. And then along come the editors and the exploratory engineers.

"This doesn't work. You need to rephrase that. This part isn't useful.
And wouldn't it be better to explain it this way?" Exploratory engineering is very likely to annoy and anger scientists.

To the extent that exploratory engineering is rigorously grounded in science, scientists can evaluate it -- but only in the sense of checking its calculations. An editor should check her work with the author. But she should not ask the author whether he thinks she has improved it; she should judge how well she did her job by the reader's response, not the writer's. Likewise, if scientists cannot show that an exploratory engineer has misinterpreted (misapplied) their work or added something that science cannot support, then the scientists should sit back and let the applied engineers decide whether the theoretical engineering work is useful.

Molecular manufacturing researchers practice exploratory engineering:
they design and analyze things that can't be built yet. These researchers have spent the last two decades asking scientists to either criticize or accept their work. This was half an error: scientists can show a mistake in an engineering calculation, but the boundaries of scientific practice do not allow scientists to accept applied but unverified results. To the extent that the results of theoretical applied science are correct and useful, they are meant for engineers, not for scientists.

Drexler is often accused of declaring that nanorobots will work without ever having built one. In science, one shouldn't talk about things not yet demonstrated. And engineers shouldn't expect support from the scientific community -- or even from the engineering community, until a design is proved. But Drexler is doing neither engineering nor science, but something in between; he's in the valuable but thankless position of the cultural ambassador, applying scientific findings to generate results that may someday be useful for engineering.

If as great a scientist as Lord Kelvin can be wrong about something as mundane and technical as heavier-than-air flight, then lesser scientists ought to be very cautious about declaring any technical proposal unworkable or worthless. But scientists are used to being right. Many scientists have come to think that they embody the scientific process, and that they personally have the ability to sort fact from fiction. But this is just as wrong as a single voter thinking he represents the country's population. Science weeds out falsehood by a slow and emergent process. An isolated scientist can no more practice science than a lone voter can practice democracy.

The proper role of scientists with respect to molecular manufacturing is to check the work for specific errors. If no specific errors can be found, they should sit back and let the engineers try to use the ideas.

A scientist who declares that molecular manufacturing can't work without identifying a specific error is being unscientific. But all the arguments we've heard from scientists against molecular manufacturing are either opinions (guesses) or vague and unsupported generalities (hand-waving).