yadi hi satyatvamithyātvavyatirekeṇa śabdānāṃ rāśyantaraṃ na syāt, tadaikarāśyabhāve dvitīyarāśisadbhāvo nāntarīyakaḥ syāt
If indeed there were no other category for words besides truthfulness and falsity, then in the absence of one category, the presence of the second category would necessarily follow.