Modem Western culture understands itself as the foremost bearer of rationality, and this self-understanding rests upon the twin pillars of science and technology. From one perspective, that in which knowledge claims are recognized as the primary location for rational evaluation, science looms larger. In its light the posits of scientific theory, more than any other form of understanding, gain support from rational evaluative canons. They offer the best account we have of the nature and ways of the physical world, and consequently provide the theoretical underpinning of technological success and advance. From another perspective, that in which rational evaluation pertains in the first instance to actions designed to enhance the exercise of our designs upon the world, technology is in the foreground. Then science gains rational precedence as a form of understanding because it provides the theory that furthers technological practice.