WE LIVE IN HUME'S WORLD, NOT DESCARTES':

Physicist Richard Feynman had the following advice for those interested in science: "So I hope you can accept Nature as She is--absurd."1 Here Feynman captures in stark terms the most basic insight of modern science: nature is not understandable in terms of ordinary physical concepts and is, therefore, absurd.

The unintelligibility of nature has huge consequences when it comes to determining the validity of a scientific theory. On this question, Feynman also had a concise answer: "It is whether or not the theory gives predictions that agree with experiment. It is not a question of whether a theory is philosophically delightful, or easy to understand, or perfectly reasonable from the point of view of common sense."2 So put reasonableness and common sense aside when judging a scientific theory. Put your conceptual models and visualizations away. They might help you formulate a theory, or they might not. They might help to explain a theory, or they might obfuscate it. But they cannot validate it, nor can they give it meaning.

Erwin Schrödinger made a similar critique of the simplified models widely used to explain scientific concepts in terms of everyday experience, such as those used to illustrate atomic theory:

A completely satisfactory model of this type is not only practically inaccessible, but not even thinkable. Or, to be more precise, we can, of course, think it, but however we think it, it is wrong; not perhaps quite as meaningless as a "triangular circle," but much more so than a "winged lion."3

"Do the electrons really exist on these orbits within the atom?" Schrödinger asks rhetorically. His answer: "A decisive No, unless we prefer to say that the putting of the question itself has absolutely no meaning."4

Feynman and Schrödinger were concerned about the extremely small scale, but what about the extremely large scale? A single human cell has more than twenty thousand genes. Therefore, assuming one protein per gene, the number of different non-modified proteins exceeds twenty thousand. Add to that the many more different proteins resulting from alternative splicing, single nucleotide polymorphisms, and posttranslational modification. No conceptual model is conceivable for the interactions among all of these genes and proteins, or for even a tiny portion of them, when one considers the complex biochemistry involved in regulation. What is the meaning of the intricate and massive pathway models generated by computer algorithms? Is this even a meaningful question to ask? And the human body contains on average an estimated thirty-seven trillion cells!

Yet science has had great success dealing with the unthinkable and inconceivable. Hannah Arendt puts the matter succinctly: "Man can do, and successfully do, what he cannot comprehend and cannot express in everyday human language."5 We have mathematically sophisticated scientific theories and daily operate with advanced engineering systems that are physically incomprehensible and whose principles cannot be communicated in everyday language. In Kantian terms, we are not limited by human categories of understanding.

This radical disconnect between scientific theory and everyday human understanding became impossible to ignore in the twentieth century. During that time, grappling with the issue of internal model randomness, as exemplified by quantum theory in physics, brought this problem to the fore.

Today, scientists are grappling with the problem of model uncertainty, as seen in areas like climate and medicine. These questions are increasingly challenging the basis of modern scientific knowledge itself, which is defined by a combination of mathematics and observation. Modern scientific knowledge, while rejecting commonsense conceptual models, has always depended upon mathematically expressed theories that could be validated by prediction and observation. But this approach is now under pressure from multiple sides, suggesting a deep crisis of scientific epistemology that has not been fully confronted. At the same time, political leaders find themselves increasingly impotent when faced with scientific issues. As we move further into the twenty-first century, humankind is presented with an existential paradox: man's destiny is irrevocably tied to science, and yet knowledge of nature increasingly lies not only outside ordinary language but also outside the foundational epistemology of science itself.

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