One of the earliest Scotist treatises on natural philosophy. Duns Scotus left neither a commentary on the Physics nor a systematic treatise on natural philosophy, a lacuna his followers soon sought to address. Among the first attempts to explicate a Scotist natural philosophy is the Quaestiones de formis by Petrus Thomae. Like other works in this series on Peter’s work, the De formis is dedicated to a single philosophical topic. Following an introductory question about the metaphysical aspect of form, the focus shifts to form as it functions in the process of change. Interestingly, Peter displays little interest in the classic Franciscan theories of plurality of forms, seminal reasons, or the reality of matter, providing instead detailed investigations into indeterminate dimensions and the introduction and education of forms into matter. Distinct within Petrus Thomae’s corpus is the treatise’s detailed engagement with Dominican natural philosophy, drawing not only on Thomas Aquinas but also on Hervaeus Natalis and John Quidort. Duns Scotus left neither a commentary on the Physics nor a systematic treatise on natural philosophy, a lacuna his followers soon sought to address. Among the first attempts to explicate a Scotist natural philosophy is the Quaestiones de formis by Petrus Thomae. Like other works in this series on Peter’s work, the De formis is dedicated to a single philosophical topic. Following an introductory question about the metaphysical aspect of form, the focus shifts to form as it functions in the process of change. Interestingly, Peter displays little interest in the classic Franciscan theories of plurality of forms, seminal reasons, or the reality of matter, providing instead detailed investigations into indeterminate dimensions and the introduction and education of forms into matter. Distinct within Petrus Thomae’s corpus is the treatise’s detailed engagement with Dominican natural philosophy, drawing not only on Thomas Aquinas but also on Hervaeus Natalis and John Quidort.