Anyone who has studied linguistics in the last half-century has been affected by the work of David Perlmutter. One of the era's most versatile linguists, he is perhaps best known as the founder (with Paul Postal) of Relational Grammar, but he has also made contributions to areas ranging from theoretical morphology to sign language phonology. Hypothesis A/Hypothesis B (the title evokes Perlmutter's characteristic style of linguistic argumentation) offers twenty-three essays by Perlmutter’s colleagues and former students.