In order to enhance indexing as a science and perhaps pave the way for further advances in indexing technology, it is desirable for those who create indexes to reflect now and then on the fundamental objectives of their work. The concept of usefulness of indexes is discussed, and is shown to be highly subjective. Usefulness depends on the values and motives of the index users or evaluators, and is not inherent in the index alone. Publishers are a very important class of evaluators of indexes. Publishers’ values and motivations deserve the attention of indexers. The low regard that many publishers have shown for indexes as enhancers of book sales and profitability may well have been justified in the past. However, the advent of online bibliographic database services now makes it possible for enterprising publishers to profit by using book indexes for the secondary, or even alternate, purpose of enhancing online database services and thus attracting new readers and purchasers for books long after their original dates of publication.