+How can we know that an object with certain properties exists? In the previous chapter, we saw that it suffices to give an example of such an object, but finding an example might be a hard problem. One way to find an example is to go through all objects and check whether at least one of them meets the requirements. However, in many cases, the search space is enormous. A computer may help, but some reasoning that narrows the search space is important both for computer search and for “bare hands” work. In this chapter, we will learn various techniques for showing that an object exists and that an object is optimal among all objects (say, the smallest or largest object that meets the requirements).
0 commit comments