 … [Proclus] says that angles ACF and angle ACE are equal to two right angles, to which you respond that such angles should be added separately and not in terms of one being part of the other, and that in this way, they are equal to two right angles. We had already come to that response to in previous discussion on the matter, and we agree that we have refuted it [Proclus] satisfactorily. Nevertheless, we will demonstrate it now with greater clarity. (LC: 301: #12)