Consider some of these generalizations that I came up with as I thought about this. Important events have many causes, many antecedents, many things that preceded them. Consider a technique like computed tomography. Consider all the work by all the different people that have gone into developing that particular technique. So the event of the discovery and development of computed tomography had many things it depended upon.
Events often cause each other.
Things do not happen in isolation. For us up to this point, there has been great pressure to use technology in medicine. Any time a technological innovation is discovered, it is rapidly adopted by the medical profession. Again, I'll use computed tomography as an example. By the time the EMI scanner was first made available in the United States in 1972, within four years computed tomography was a common finding in major U.S. hospitals.