 Since “the primary underlying subject seems most of all to be substance” (1029a1–2), because what is said or predicated of it depends on it, the investigation begins with this subject, quickly isolating three candidates: the matter, the compound of matter and form, and the form itself (1029a2–3), which is identical to essence (1032b1–2). Almost as quickly (1029a7–32), the first two candidates are at least provisionally excluded. A—perhaps the—major ground for their exclusion is the primacy dilemma, which we shall now briefly investigate.