This book by Carson Schütze poses an important question. Are grammaticalityjudgments a reliable source of data for linguistic theories? Grammaticality judgments, reliable ornot, have been the main, and most often the only, source of data in linguistic theory for manyyears. “‘Because many of the relevant structures are fairly complex and simplymight not arise in the normal course of conversation, or during observation by anexperimenter' (White, 1989, p. 58), UG [Universal Grammar] researchers havegenerally 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 todraw on speakers' intuitions about their competence. Grammaticality judgments consist ofquestions about whether a sentence is grammatical according to native speakers. Most often, thenative speaker is the linguist her- or himself as the only subject. Not only can bias exist whenlinguists are the source of data for her or his own theories, but also relying on the intuitions ofonly one speaker limits the credibility of the theory. When more than one speaker is queried, ithas been shown that consistency is not always guaranteed: variation among and within speakersis a common feature in judgments (Mohan, 1977; Snow & Meijer, 1977). Idiosyncrasies ofthe subjects, presentation of the material, and experimenter's procedure are among thefactors that contribute to this variation in judgments. An underlying problem in linguistictheorizing comes from the fact that linguists are normally not “trained in methods forgetting 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 linguistswith answers to the following questions. What information about language can grammaticalityjudgments offer? What factors affect the form of these judgments? What can be done to make thebest use of these judgments?