Wahdaniyya · tawhid
Oneness
Tamanu': God is one, indivisible, in need of nothing
Why can there not be two creators?
وَلَا شَيْءَ مِثْلُهُ، وَلَا شَيْءَ يُعْجِزُهُ، وَلَا إِلَهَ غَيْرُهُ
There is nothing like Him; nothing can overpower Him; and there is no deity besides Him.
One — by an argument of reason
The center of the whole creed is : God is one, single, in need of nothing. Classical expresses this oneness through the argument of mutual prevention — al-tamanu'. Were there two creators, the will of one could meet the resistance of the other — and yield to it in even one thing; but the one who yields is incapable, and incapacity is incompatible with godhood. The very possibility that one could be prevented strips away perfect power — and God is exalted above deficiency. This reasoning needs no experiment: it stands on reason alone.
And this oneness is of a special kind. God is not "one among many" and is not assembled out of parts: He is indivisible, and nothing beside Him shares existence with Him. All that you have met along the path is His creation and His signs; He is not among them, not the first in a row. To this One the whole spine is drawn: the attributes that shone in the halls are His attributes.
from the kalam
هَذَا وَصْفٌ لَهُ بِكَمَالِ الْقُدْرَةِ، لِأَنَّ وُجُودَ كُلِّ مَوْجُودٍ سِوَاهُ بِإِيجَادِهِ، فَمُحَالٌ أَنْ يُعْجِزَهُ شَيْءٌ، فَإِنَّ الْعَجْزَ نَقْصٌ، وَاللَّهُ مُنَزَّهٌ عَنِ النَّقَائِصِ
This is a description of Him by perfect power. Everything that exists besides Him exists because He gave it existence. So it is impossible for anything to overpower Him: incapacity is a deficiency, and Allah is exalted above deficiencies.
Here there is no scientific exhibit: of God's oneness science is silent. A single law of the sky, the same spectra and constants out to the edge of the observable world, are not "a sign of one Creator": the uniformity of law would be accepted just as readily by a picture with many gods, and by one with no God at all. Dalil al-tamanu' stands on reason, not on a telescope.
And so it is with all the "quiet" halls of the path: where an attribute has no scientific exhibit, the hall names the silence. Not every truth needs a telescope. Oneness is the anchor to which the whole path is drawn; it holds on its own, without props from physics.