So instead of concentrating on what isn't science, I thought I might add a few words on science as a framework of reasoning and for making sense of a complex world. The value of science isn't just in the spinoffs, the application of the results of science, but as a concerted endeavour to understand the whole universe, from the stars, the ground upon which we walk, the life around us, and to the ends of time. My thoughts are very general and broad, there are exceptions to everything of course but in the main, I think science as a whole possess the following properties.
Science is a process. To make a tenuous analogy, the economy is a process, rather than an object. Science is continually evolving, it changes in response to many factors, some internal, but most importantly to external input, observation and experiment. Without this, science would be a sterile, onanistic activity. There are no received truths, the final arbiter is nature itself. Science is both reactive and proactive. Reactive in the sense that science must continually accommodate new results. Proactive in that it seeks to find the new results which would change science itself. The least interesting science is where there is nothing new to discover.
Science is introspective. Science is not, contrary to popular perception, about absolute certainty and truth. The hallmarks of a vigorous science is constructive debate and discussion. By subjecting our theories and results to the greatest scrutiny, the more confident we can be about their reliability if they pass these tests. What may seem to outsiders like indecision, qualification, dithering and caution, is actually thoughtful consideration of the complexities of the subject. It's not a case of right or wrong usually, rather a case of less or more valid in a particular context. This can be confusing to an outsider who expects the opposite.
Science is like betting. A good punter studies the form, tries to gather as much information about past performances as well as takes into account current conditions to make an informed guess as to future performance. This is what science does with the world. It studies how the world works and tries to infers the mechanisms by which it functions and hence hopefully how it will work in given circumstances. Our theories are bets on what would happen. The more learn about the world, the more we can refine our models and be more confident about our wagers. Let's give a simple example, related to Dawkins' famous quote (River Out of Eden):
Show me a cultural relativist at thirty thousand feet and I'll show you a hypocrite. Airplanes are built according to scientific principles and they work. They stay aloft and they get you to a chosen destination. Airplanes built to tribal or mythological specifications such as the dummy planes of the Cargo cults in jungle clearings or the bees-waxed wings of Icarus don't.
Why do we generally not step off the edges of cliffs? It's because it is a reasonable assumption that gravity exists and rapid deceleration at the end one's vertical journey is not good for the human body. Why do we think that it is reasonable to "believe" in gravity? Not because we have Einstein's Field Equations but because historically, objects which are without support generally accelerate towards the ground. Science is just a small step further from this in that it is a systematic way of coming to a justifiable or reasonable assumption about how things will behave. If you're even slightly curious, you may want to investigate how long it take an object to fall a certain distance. You could extend this to the case when you give the object some initial velocity. How about horizontal velocity etc? Galileo did some experiments and came up with a set of rules which seemed to describe the trajectory of ballistic objects. The ancient Greek philosopher Aristotle had some ideas on the same subject. However, he based his conclusions on how objects ought to behave, rather than how they actually do behave. Unsurprisingly, ballistic trajectories envisioned by medieval engineers and gunners based upon Aristotelian ideas were inconsistent with Galileo's calculations, and what were later incorporated in Newton's Laws of Motion.
Science is a process by which we come to such conclusions about the world. However, these conclusions are aren't absolute truths, each comes with their own caveats and degrees of certainty, depending upon the results, theory and the interplay between them, and how they fit within the entire structure of scientific thought. Some scientific conclusions are so certain that it would be perverse to believe otherwise, e.g. the fact of gravity. Similarly certain conclusions are that the Earth is not flat, the Earth revolves around the Sun, the existence of atoms, evolutionary change, and local realism is not a good physical model. Down the spectrum, there are conclusions which are less certain, but still reasonable to take as working hypotheses, the Standard Model of particle physics is one example. At the edge of what could conceivably be called science (rather than mathematical speculation) is String Theory.
One could liken this attitude to Bayesian analysis. Given all the observations and experiments that have ever occurred, what is the post priori probability that a given outcome is likely? Science represents our best guess given everything we know (not to mention a consistent framework in which to place such knowledge in context). Being unscientific is ignoring the evidence and betting on the outsider when the payoff is not worth the risk (cf. MMR).
I think it's important to try to impress upon the public why scientists accept the validity of their results, and why they all come with degrees of uncertainty. I guess it's a fundamental worldview in which one have to accept that issues are not black and white, we live in a complex world and that its explanations may not be reducible to a sound bite. However, we're instinctual creatures, prone to acting on gut feelings about what is "right" or "wrong". Getting the public to fight our natural human instincts and be rational may be the greatest continuing battle for science.