"Causes often arrange themselves in a series. For example, let us suppose that we have a situation in which A is the cause of B. Next, we note that B is in turn the cause of C. We end up with a sequence that can be diagrammed as follows:  A--> B --> C.  Let us next suppose that C represents a problematic state of affairs that calls for a quick remedy. Knowing that C has been caused by B, we decide to concentrate our attention on B, guided by the principle that the correct way to deal with problems is to get at their causes. The logic being followed here is commendable as far as it goes, but it does not go far enough. While it is true that B is the immediate cause of C, it is not its ultimate cause. The causal sequence begins with A, and therefore that is the source of the problem C." —from D. O. McInerny, On Being Logical, Random House, 2004, pp. 33-34