Fields such as business, industry, sports, science, and performing arts incorporate some notion of what into their measuring systems?
Time has long been a major subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems. Some simple definitions of time include "time is what clocks measure", which is a problematically vague and self-referential definition that utilizes the device used to measure the subject as the definition of the subject, and "time is what keeps everything from happening at once", which is without substantive meaning in the absence of the definition of simultaneity in the context of the limitations of human sensation, observation of events, and the perception of such events.
The predominant school of thought in the 13th century was the Thomistic reconciliation of the teachings of Aristotle with Christian theology. The Condemnation of 1277, enacted at the University of Paris, placed restrictions on ideas that could be interpreted as heretical; restrictions that had implication for Aristotelian thought. An alternative was presented by William of Ockham, who insisted that the world of reason and the world of faith had to be kept apart. Ockham introduced the principle of parsimony – or Occam's razor – whereby a simple theory is preferred to a more complex one, and speculation on unobservable phenomena is avoided.