The Origin of Knowledge
We (and all other organisms) are born into a universe that we already "know" on some level, even without having had any individual experience at all. It's in our genes. The genes contain detailed instructions for building a sensory apparatus that is precisely tuned to the signals which an organism needs to receive and process in order to function
properly, that is, to survive, to grow, and to reproduce.
Concerning our own senses, we have eyes to see the electromagnetic radiation emitted by the sun (called "light") and reflected off objects. We have ears to hear vibrations transmitted through the air (called sound). We have a sense of smell that can make an instantaneous analysis of molecules dissolved in air or water, and which is highly sensitive toward certain compounds (hydrogen sulfide being one that can be detected at extremely low levels). Our eyes cannot see ultraviolet, although the eyes of many insects can. Our ears cannot hear extremely high-pitched notes, although the ears of bats can. Our nose is no match for that of a dog. And we have no sense for telling north from magnetism (as some birds have) or for disturbance of the electric field around us (as eels and rays do). For details on our senses, see the off-curriculum (off quiz) table at Handbook of Medical Informatics, and details on our eyes at Photo.net .
Thus, what we think of as the "real" world around us is actually a rather specialized representation of this world, which is produced by the senses we happen to have and rely on. If we could sense infrared (like pit vipers) our world would be different (as so strikingly illustrated in the movie "Predator" which featured an alien from outer
space hunting people using their body heat as a signal). We say "I see" when we understand, because our models of the world around us depend on our sense of sight. Nothing has expanded our understanding of the world more than using microscopes to look at the invisibly small, and telescopes to look at the barely visible and the invisible at great distance.
So, we build our models of the world around us based on sight. Most of us see three colors in addition to shades of gray, and our brain puts together a rich palette of intermediate colors of every hue. We believe this is what the world is like, because that is what it "looks" like. In reality, it is our interaction with the world, our response to the
stimulus of signals form it, that we use to build our "world model". Because our experiences differ, every person on this planet has a different world model, a kind of "private universe."
In addition to the information received through our senses there is tradition, that is, the things other people (to begin with, our parents and teachers) tell us about the world. Most of what we know (or think we know) about the world around us was told to us by others. The set of beliefs passed on from one generation to the next makes up "culture". Being human means being part of a culture. It is hard to “know” things that you do not also believe.
Science is not about listing things that are true, but about finding ways to discover things that might be true, and ways to prove that things claimed to be true actually are not. Three types of feats are counted as success in the making and breaking of hypotheses. One, to present a hypothesis, which can be falsified in principle, but survives all attempts to kill it. Two, to destroy a hypothesis which has been generally accepted as valid, because it has stood up a long time. Three, to find evidence to strengthen and refine some very uncertain hypothesis. All three feats, of course, will produce more notice if the hypothesis in question is important than if it does not matter very much.
Science is about making our universes less private and more generally accepted, even across cultures. This very same goal is pursued by tradition, within each culture, which fosters general belief systems, which are often at odds with the observations of modern science. Thus, when science defends its world-view, invoking observation, it comes up against older claims of world knowledge. These older claims have deep historical roots. What makes the scientific method exasperating to those whose world view it imperils is that it disregards any claim based on tradition (at least in principle) and demands that each claim be subject to challenge. It is a kind of Freedom-of-Information act, translated into the realm of general knowledge and claims to knowledge. Most of the challenges, in fact, are not between scientists and nonscientists, but are within science itself. Science is not so much a body of knowledge as it is an ongoing discussion on what is acceptable (for now) and what is not.