فَصْلٌ فِي التَّناقُضِ
التَّناقُضُ اخْتِلافُ قَضِيَّتَيْنِ بِحَيْثُ يَلْزَمُ لِذاتِهِ مِنْ صِدْقِ كُلٍّ كَذِبُ الأُخْرَى وَبِالعَكْسِ، وَلا بُدَّ مِنَ الاخْتِلافِ فِي الكَيْفِ وَالكَمِّ وَالجِهَةِ، وَالاتِّحادِ فِيما عَداها. وَالنَّقِيضُ لِلضَّرُورِيَّةِ المُمْكِنَةُ العامَّةُ، وَلِلدّائِمَةِ المُطْلَقَةُ العامَّةُ، وَلِلمَشْرُوطَةِ العامَّةِ الحِينِيَّةُ المُمْكِنَةُ، وَلِلعُرْفِيَّةِ العامَّةِ الحِينِيَّةُ المُطْلَقَةُ، وَلِلمُرَكَّبِ المَفْهُومُ المُرَدَّدُ بَيْنَ نَقِيضَيِ الجُزْأَيْنِ، لٰكِنْ فِي الجُزْئِيَّةِ بِالنِّسْبَةِ إِلَى كُلِّ فَرْدٍ.
(tanāquḍ) is a difference between two such that, by itself, the truth of each entails the falsehood of the other, and the other way round. They must differ in quality, quantity and mode, and agree in everything else. The contradictory of the necessary is the general possible; of the perpetual, the general absolute; of the general , the possible while-described (ḥīniyya mumkina); of the general conventional, the absolute while-described (ḥīniyya muṭlaqa); and of a compound, the that alternates between the contradictories of its two parts — but in the , with respect to each individual.
Tahdhīb al-manṭiq · p. 9–10