Practical experience, observation and research.

The history of science contains numerous instances where the observation of spontaneous natural or social phenomena by means of thoughtful practitioners and researchers have triggered fathomless insights that have then been articulated and proofed as a new and persuasive theory about more [i]or[/i] less aspect of the natural or social world.

For well known examples think of Darwin, his voyages and the theory of natural selection; or Archimedes, his bathtub and his buoyancy principle; of Fleming and his chance observation of the issue of Penicillium mold on bacteria cultures; or Frederick Winslow Taylor and his observations and unfolding of practices that became labelled as