2. In line 30 he makes a similar change; instead of [Greek: tô=| dikai/ô| proskei/setai kai\ tô=| ou) dikai/ô|]--he reads, [Greek: tô=| a)nthrô/pô| proskei/setai kai\ tô=| ou)k a)nthrô/pô|]. In line 38, instead of [Greek: prostethe/n], he reads [Greek: prostethe/ntos]. Of these three alterations the first appears to me good, but insufficient; the second not good, though the passage as it stands in Bekker requires amendment; and the third, a change for the worse. The purpose of Aristotle is here two-fold. First, to give the reason why, when the propositions were _tertii adjacentis_, there were two Quaternions or four couples of antithetical propositions; whereas in propositions _secundi adjacentis_, there was only one Quaternion or two couples of antithetical propositions. Next, to assign the distinction between the first and the second Quaternion in propositions _tertii adjacentis_. Now the first of these two purposes is marked out in line 25, which I think we ought to read not by substituting the words of Waitz in place of the words of Bekker, but by retaining the words of Bekker and inserting the words of Waitz as an addition to them. The passage after such addition will stand thus--[Greek: le/gô d' o(/ti to\ _e)/stin_ ê)\ tô=| dikai/ô| proskei/setai ê)\ tô=| ou) dikai/ô|, kai\ ê)\ tô=| a)nthrô/pô| ê)\ tô=| ou)k a)nthrô/pô|, ô(/ste kai\ ê( a)po/phasis. te/ttara _ou)=n_ e)/stai.] Here Aristotle declares the _reason why_ ([Greek: ou)=n]) there come to be four couples of propositions; that reason is, because [Greek: e)/sti] and [Greek: ou)k e)/sti] may be joined either with [Greek: di/kaios] or [Greek: ou) di/kaios] and either with [Greek: a)/nthrôpos] or with [Greek: ou)k a)/nthrôpos]. Both these alternatives must be specified in order to make out a reason why there are two Quaternions or four couples of antithetical propositions. But the passage, as read by Bekker, gives only one of these alternatives, while the passage, as read by Waitz, gives only the other. Accordingly, neither of them separately is sufficient; but both of them taken together furnish the reason required, and thus answer Aristotle's purpose.