This book by Carson Schütze poses an important question. Are grammaticality judgments a reliable source of data for linguistic theories? Grammaticality judgments, reliable or not, have been the main, and most often the only, source of data in linguistic theory for many years. “‘Because many of the relevant structures are fairly complex and simply might not arise in the normal course of conversation, or during observation by an experimenter' (White, 1989, p. 58), UG [Universal Grammar] researchers have generally relied on some form of grammaticality judgment (GJ) task” (Katrien & Lantolf, 1992, p. 32). Katrien and Lantolf (1992) pointed out that with this task linguists try to draw on speakers' intuitions about their competence. Grammaticality judgments consist of questions about whether a sentence is grammatical according to native speakers. Most often, the native speaker is the linguist her- or himself as the only subject. Not only can bias exist when linguists are the source of data for her or his own theories, but also relying on the intuitions of only one speaker limits the credibility of the theory. When more than one speaker is queried, it has been shown that consistency is not always guaranteed: variation among and within speakers is a common feature in judgments (Mohan, 1977; Snow & Meijer, 1977). Idiosyncrasies of the subjects, presentation of the material, and experimenter's procedure are among the factors that contribute to this variation in judgments. An underlying problem in linguistic theorizing comes from the fact that linguists are normally not “trained in methods for getting reliable data” (p. 4). All this results in theories that are not adequately supported. Nonetheless, they are used as a springboard for new theories. Schütze provides linguists with answers to the following questions. What information about language can grammaticality judgments offer? What factors affect the form of these judgments? What can be done to make the best use of these judgments?