 Drawn in such formal terms, the distinction can seem alien and difficult to grasp but the basic idea is actually not that complex. A few examples should help illustrate Nagel’s idea. Suppose that there is reason for me to phone a friend because doing so would make the friend happy. Now suppose that my reason is best expressed as follows—that phoning her would make someone happy. In that case, the fact that the person who is made happy is my friend is incidental. If phoning a stranger would have generated just as much happiness then I would have had just as much reason to call the stranger. This in turn suggests that the principle corresponding to this reason is of the form,