The general rules of science, it seems to me, are fairly clear, if not always easy to follow. Though highly structured, science is (or should be) one of the most anti-authoritarian of all human pursuits because of its insistence on evidence gathered from the greater universe, from our apparent surroundings. As time went on I became more interested in the philosophy of science. An hour spent in Zoo 400 on a Wednesday morning was sometimes both the distraction and also the high point of the day. I began to browse Jack's bookshelves; sampling some of the classics Cy had listed on the long bibliography of suggested reading he gave to the students. I discovered some quotations worth keeping.
In 1963 the well-known philosopher of science, Karl Popper, summed up his views in the title of his book, Conjectures and Refutations: The Growth of Scientific Knowledge. He clearly described what I believe to be a central theme, a piece of the soul of science, early on in his book (pp. 29-30):
"What we should do, I suggest, is to give up the idea of ultimate sources of knowledge, and admit that all knowledge is human; that it is mixed with our errors, our prejudices, our dreams, and our hopes; that all we can do is to grope for truth even though it is beyond our reach. We may admit that our groping is often inspired, but we must be on guard against the belief, however deeply felt, that our inspiration carries any authority, divine or otherwise. If we thus admit that there is no authority beyond the reach of criticism to be found within the whole province of our knowledge, however far it may have penetrated into the unknown, then we can retain, without danger, the idea that truth is beyond human authority. And we must retain it. For without this idea there can be no objective standards of inquiry; no criticism of our conjectures; no groping for the unknown; no quest for knowledge."
So, truth is the ultimate goal that science must always have, but we scientists can never quite touch it, and we must remain aware that we can never quite touch it. According to Popper, we can figure out when we're wrong with reasonable certainty, but we can never know if we have fully captured the truth. We must always settle for the asymptote, the ever-more-accurate description of the world around us, and the next best guess we can make to explain it. An apparent weakness, an inability to "know the truth," is strength in disguise, and it is what makes science (and accompanying technology) so fertile. Instead of "true" versus "false" we work with "probably false" versus "not demonstrably false" or "possibly true." There can be good negative proof and good positive evidence, but there is no absolute positive proof. Ever. This makes the framework of science asymmetrical and open-ended, Popper argued, always subject to further criticism and exploration.
In the more spiritual realms of metaphysics, including many religions, there is a reliance on "truths" that arise directly from faith, but these "truths" do not require evidence. If one needs hard evidence beyond the confines of whatever beliefs one prefers, I suppose such a person can't be much of believer. Scientists chase the "truth" of what we assume to be objective reality in the natural world, but can never quite catch it - the search is never-ending. Have faith or demand evidence? These two views are not necessarily in conflict and are not mutually exclusive, but they are still different. The danger comes when the two are confused.
Science is often a deeply creative business, but it is also very restrictive. One primary rule is that clear evidence, however annoying, cannot be ignored. For instance, the evidence that evolution has, somehow, occurred is simply undeniable to a scientist - it is everywhere. This assertion says nothing about religion one way or another, nor does it say anything about the causal forces underlying evolution, or about any particular theory, including Darwin's. Science can't address questions about deities or prophets. It's possible that creationists are correct in their assertion that what we see in the biological world, past and present, resulted from divine intervention, that all of our fossil collections, dating methods, and other sources of data are wrong. God slapped down the entire, massive body of evidence from which scientists infer evolution in a few thousand years? Well, maybe. There's no way such a possibility can be scientifically falsified, since gods and their miracles are not subject to empirical testing, but that's not what any of the evidence tells us. Every bit of available evidence in the in the natural world we inhabit repeatedly corroborates the events and patterns of evolution, and there's no pretending otherwise. Jack liked to point out that the evidence in the living world presents us with a hierarchy of forms, sets of organisms of greater and lesser similarity. This observation led Linneaus to his original classification and naming of plants and animals. It developed into what is called comparative biology, and seeks its scientific justification in information theory; evolution, descent with modification, is just an additional description of the results of comparative biology.
Creation myths, all of them, are just that - imaginary, alternative realities. They are often interesting, perhaps reflecting particular human cultures, but they lack evidence. Myths attempt to account for the origins of what we see around us, but are beyond empirical examination. Various creation myths account for the surroundings in which different groups of people found themselves, and they rely on some understanding of that natural world. Myths inhabit the world of comparative religion or anthropology, where one can consider the stories of creation from one culture and compare them with others without being critical of the story itself. Genesis, where God makes all the life forms and develops the first human from a lump of clay, is an interesting story. In the legends of some coastal tribes of the Pacific Northwest, Raven coaxes the first little humans out of a large clamshell he finds on the beach, and this is an equally interesting story. You can believe one over the other, but the choice is based on faith or upbringing, not on evidence. On the one hand, the evidence for the occurrence of evolution is everywhere, though the causal driving force is arguably less clear. On the other hand, Darwin's particular ideas about the causes of evolution, and those of some of his latter day disciples, are too often presented not as theory or conjecture, but as a revealed, understood truth. Natural selection is not to be seriously criticized or questioned as an important causal force; it is to be believed. This is authoritarian. This is a religious, not a fully critical, scientific exploration of evolution, and it has plagued biology for a very long time.
A keystone of science, I think, is that scientists are allowed only one "hard" foundation of belief; one valid assumption while they are practicing science. Scientists must assume the existence of some sort of objective reality, where the energy, objects, forces and interactions of the universe would all be happening without an observer. Of course, that could be wrong, too. We could all be having a collective hallucination. But if we don't assume an objective reality, what reason would we have for wanting to describe and understand our surroundings when our world and our observations of it are all just dreams? There would be no reason to do science, no inspiration, and no point to our passionate curiosity if we didn't believe we were describing objects and events that exist beyond us and without us. It has been argued that the presence of the observer alters the observation, and even the thing or event being observed. This may be of some concern to at the scale of the very tiny, but as my friend and early readers, Ruth Deery, put it, "...it is not implied that the astronomer makes any difference in the behavior of Betelgeuse, or in the rate and flow of a river or the acceleration of a falling body." It is necessary that we make observations, look for patterns and correlations, offer explanations, draw conclusions, reject some of them, and continue building on our knowledge.
Given that some sort of objective reality exists, we try to organize our perceptions around the regularities that appear to be part of it. Where, given appropriate conditions, comparable events occur over and over again, we can begin to surmise they are the result of a "law." Our understanding of these regularities or laws is pretty poor, but as we build, test and modify theories, the accuracy of our descriptions of nature grows. We try to describe laws, and then base theories and hypotheses on them. We compare our theories against evidence, modify the theories, and then take another look. Laws (regularities of nature), theories (larger scale explanatory accounts) and hypotheses (more local guesses about the material world) are all made of "soft" assumptions - all are subject to further interpretation and change, but we can (and must) assume their validity, at least temporarily, in order to build on them. The only "hard" assumption that must be made is the existence of objective reality itself. We may understand little of trees, forests, gravity or sound waves moving through the atmosphere, but we assume the tree produces waves and makes a noise when it falls, regardless of the presence of a listener to hear the sound. This does not mean that our interpretations of observations are not "theory-laden," where we see what we would like, or expect, to see. But the structure of science is intended to guard against this, albeit not always successfully, because we are mere humans and can't help but tend to lean toward our own favorite ideas. When we pursue it honestly, science serves us well by helping to keep us honest.