On the generalized theory of gravitation

The editors of Scientific American have asked me to write about my recent work which has just been published. It is a mathematical investigation concerning the foundations of field physics. Some readers may be puzzled: Didn't we learn all about the foundations of physics when we were still at school? The answer is "yes" or "no," depending on the interpretation. We have become acquainted with concepts and general relations that enable us to comprehend an immense range of experiences and make them accessible to mathematical treatment. In a certain sense these concepts and relations are probably even final. This is true, for example, of the laws of light refraction, of the relations of classical thermodynamics as far as it is based on the concepts of pressure, volume, temperature, heat and work, and of the hypothesiS of the non-existence of a perpetual motion machine. What, then, impels us to devise theory after theory? Why do we devise theories at all?