— Augustin-Jean Fresnel French engineer and physicist 1788 - 1827
Context: If one was sometimes led astray by trying to simplify the elements of a science, it is because one has established systems before putting together a fairly large number of facts. Some assumption, which would be very simple when one considers only a class of phenomena, requires many other assumptions if one wants to leave the narrow circle in which we had initially withdrawn. If nature has offered to produce the maximum effect with minimum causes, it is in all of its laws that it had to solve this major problem. It is without doubt difficult to discover the foundations of this wonderful economy, i. e. the simplest causes of phenomena considered from such a wide point of view. But if this general principle of the philosophy of physics does not lead immediately to the knowledge of truth, it can direct the efforts of the human spirit, by leading it away from theories which relate the phenomena to too many different causes, and by adopting preferably those based on the smallest number of assumptions, which show to be more fruitful in consequences.