IN THE NEW BOOK BY STEPHEN HAWKING AND Leonard Mlodinow, The Grand Design, the authors manage to give a detailed historical summary of mathematics and physics, explain tile complexities of various mathematical models and theories that relate to the universe and its origin, and also find time to declare both philosophy and god to be dead. And they do all of this within just 181 pages of text. That a book so comprehensive is so comprehensible is a wonder. Yet, the presentation of the most important idea in the book, "Model Dependent Realism" (MDR), may leave readers thirsting for a more detailed explanation. MDR, after all, does not just provide an important perspective for analyzing physical models of the universe; it also solves most or all of the philosophical conundrums and paradoxes that have vexed deep thinkers for centuries.
MDR is really the end result of the Einsteinian Revolution. Einstein noted that when making scientific and mathematical equations, one must take into account both the observation and the observer. MDR carries this notion to its logical conclusions. To begin with, our senses evolved to make models out of sensory data in the outside universe. Those models evolved not for the purpose of giving us a clear sense of the workings of the universe, but for evolutionary purposes, such as helping us to survive and reproduce. (Pre-Darwinian Enlightenment philosophes fretted over being limited by their senses, but lacked the insights that evolutionary biology later added.) Ancestors incapable of absorbing the light from a tightly packed group of molecules we call a rock, and forming that light into a model that registers in the mind as "rock," would likely have found themselves removed from the gene pool.
All macro-organisms that survive have to find some way of detecting the sensory data around them, but the way in which those data are registered is somewhat arbitrary and likely has to do with whatever an original random mutation found useful. For example, think of a rotting carcass on a hot summer day. Clearly, the carcass is giving off sensory data, but humans find that data repulsive because the meat would make us sick, but for vultures and flies the gas is the olfactory equivalent of a dinner bell. There is "material" there (the gas) but each organism makes its own "model" based upon that real substance. As Hawking and Mlodinow note:
Our sun radiates at all wavelengths, but its radiation is most intense in the wavelengths that are visible to us. It's probably no accident that the wavelengths we are able to see with the naked eye are those in which the sun radiates the most strongly: It's likely that our eyes evolved with the ability to detect electromagnetic radiation in that range precisely because that is the range of radiation most available to them. (p. 91).
Once it is understood that our "mind models" are the result of evolutionary processes much else becomes clear. Memories, for example, are just images in the mind. As Julian Barbour has pointed out, humans never really have more than just a "now" in which we live. (Defining the "now" is problematic, but for our purposes here it will suffice to say it's the shortest amount of time that a coherent thought or realization can exist. Psychologists such as Steven Pinker estimate this time to be about three seconds.) At each "now" we can conjure up images in our mind. But how do we know that those images represent the past rather than say, the future? What if we can see the future but not remember anything? What if our history books are actually books about what will happen in the future as technology gets less and less complex and archeologists are studying the distant future? From an evolutionary perspective it is reasonable to assume that memories are connected to the past because it is hard to see how it would be evolutionarily useful for an organism to view outside "reality" …