In English the nonfinite form is simply a bare verb, but in languages with a morphological distinction it usually takes the form of an infinitive. During the relevant stage the child, unlike an adult, sometimes uses an infinitive as the main verb of a root clause. Luigi Rizzi and certain other researchers therefore favor the term "root infinitives". In contrast Kenneth Wexler prefers the term "optional infinitive", highlighting his analysis of these forms as a grammatical option appearing alongside correctly inflected forms. What to call them, and why they appear the way they do, has occupied a great deal of thought, and theories of this phenomenon are still being energetically debated. Relatively early in the study of children's nonfinite forms, Colin Phillips undertook an intensive review of the available data from a wide range of languages. He developed and argued for the theory that children's apparently nonfinite forms are actually syntactically fully finite, in accord with the target grammar. For children, however, the task of combining the verb root with the appropriate inflectional morphology is not yet overlearned and automatic. The result, he proposed, is that children's productions sometimes lack this step. In other words, the children's nonfinite forms result from performance factors, and not from a lack of grammatical competence. The authors think that both the impressive array of data he surveyed and his theoretical proposal are important enough to the continuing debate on optional/root infinitives (O/RIs) that his work should be accessible to a wider audience. Phillips' careful cross-linguistic survey of children's production of O/RIs, summarized in 5 figures and 23 tables, along with his clearly stated counting procedures has been an invaluable contribution to the field.