[extract] … The sesquicentennial of the American Association for the Advancement of Science is a good time to acknowledge that science is no longer the specialized activity of a professional elite. Nor is it a philosophy, or a belief system, or, as some postmodernist thinkers would have it, just one world view out of a vast number of possible views. It is rather a combination of mental operations, a culture of illuminations born during the Enlightenment four centuries ago and enriched at a near-geometric rate to establish science as the most effective way of learning about the material world ever devised. The sword that humanity finally pulled, it has become part of the permanent world culture and available to all.

“Science, to put its warrant as concisely as possible, is the organized systematic enterprise that gathers knowledge about the world and condenses the knowledge into testable laws and principles.”* Its defining traits are first, the confirmation of discoveries and support of hypotheses through repetition by independent investigators, preferably with different tests and analyses; second, mensuration, the quantitative description of the phenomena on universally accepted scales; third, economy, by which the largest amount of information is abstracted into a simple and precise form, which can be unpacked to re-create detail; fourth, heuristics, the opening of avenues to new discovery and interpretation.

And fifth, and finally, is consilience, the interlocking of causal explanations across disciplines. “This consilience,” said William Whewell when he introduced the term in his 1840 synthesis The Philosophy of the Inductive Sciences, “is a test of the truth of the theory in which it occurs.”† And so it has proved within the natural sciences, where the webwork of established cause and effect, while still gossamer frail in many places, is almost continuous from quantum physics to biogeography. This webwork traverses vast scales of space, time, and complexity to unite what in Whewell's time appeared to be radically different classes of phenomena. Thus, chemistry has been rendered consilient with physics, both undergird molecular biology, and molecular biology is solidly connected to cellular, organismic, and evolutionary biology.

The scales of space, time, and complexity in the explanatory webwork have been widened to bracket some 40 orders of magnitude. Consider, for example, the webwork's reach from quantum electrodynamics to the birth of galaxies; or the great breadth it has attained in the biological sciences, which are not only united with physics and chemistry but now touch the borders of the social sciences and humanities.