There is a central group of ideas that underlies our understanding of the process of convection in the earth's solid mantle. These ideas are that the earth is very old, that temperatures and pressures are high in the earth's interior, and that given high temperature, high pressure and sufficient time, solid rock can flow like a fluid. As well there is the idea that the earth's crust has been repeatedly and often profoundly deformed and transmuted. This idea is a central product of several centuries' practice of the science of geology. It is the perceived deformations of the crust that ultimately have led to the development of the idea of mantle convection, as their explanation. Our subject thus connects directly to more than two centuries' development of geological thought, especially through crustal deformation, heat, time and the age of the earth.

I think we scientists should more often examine the origins of our discipline. In doing so we gain respect for our scientific forebears and we may encounter important neglected ideas. We will usually gain a perspective that will make us more effective and productive scientists. Looking at our history also helps us to understand the way science is done, which is very differently from the hoary stereotype of cold logic, objectivity, ‘deduction’ from observations, and inexorable progress towards ‘truth’.

We may be reminded also that science has profoundly changed our view of the world and we may feel some humility regarding the place of humans in the world.