Four pillars of faith and unbelief
Nahj al-Balāgha|Volume 1|Book 3|Chapter 31
وَالشَّكُّ عَلَى أَرْبَعِ شُعَب: عَلَى التَّمَارِي وَالْهَوْلِ وَالتَّرَدُّدِ وَالِاسْتِسْلَامِ فَمَنْ جَعَلَ الْمِرَاءَ دَيْدَناً لَمْ يُصْبِحْ لَيْلُهُ وَمَنْ هَالَهُ مَا بَيْنَ يَدَيْهِ نَكَصَ عَلَى عَقِبَيْهِ وَمَن تَرَدَّدَ فِي الرَّيْبِ وَطِئَتْهُ سَنَابِكُ الشَّيَاطِينِ وَمَنِ اسْتَسْلَمَ لِهَلَكَةِ الدُّنْيَا وَالْآخِرَةِ هَلَكَ فِيهِمَا.
Doubt has also four aspects: unreasonableness, fear, wavering and undue submission to every thing. So, he who adopts unreasonableness as his way, for him there is no dawn after the night; he who is afraid of what befalls him has to run on his heels; he who wavers in doubt Satans trample him under their feet and he who submits to the destruction of this and the next world succumbs to it.