It is impossible for a formal effect to be separated from form; but to exist is a formal effect of form, for form is defined as that which gives existence (esse) to a thing; therefore it is impossible to posit existence without form. For just as it is impossible that there be white without whiteness, so it is impossible to be in act without act. But to give existence (esse) belongs to first act, which is the same as form. Therefore, from the proposition, matter exists without any form, it follows that contradictories would be simultaneously true. From the fact that matter exists, it follows that it is in act; on the other hand, from the fact that it exists without any form, it follows that it is not in act. Scotus gives some kind of answer to this, which we omit because it is a figment of his imagination, and unworthy of him.
Cajetan, Commentary on St. Thomas Aquinas's On Being & Essence, Kendziersi & Wade, trs. Marquette UP (Milwaukee, WI: 2014), p.187. Scotist-Thomist disputes are sometimes more amusing than one might think.