he saw him beating a slave of his: “Allah has greater power over you than you have over him.” Thus it is established that He has power over the man himself.

The point here is that the discussion concerns only originated things that are subject to power, not everything that can be received. If the object of power cannot exist from eternity, the existence of originated things from eternity is likewise impossible. It is therefore not valid to distinguish between something received that is subject to power and something received that is not subject to power, since both are subject to power.

Second:

One may say: the existence of an originated thing from eternity is either possible or impossible. If it is possible, then the object of power can exist from eternity. If it is impossible, then its existence is impossible both as something received and as an object of power.

Third:

One may say: affirming an object of power when that object is impossible combines two contradictories. It is therefore inconceivable to affirm power when its object is impossible; it can only be affirmed when its object is possible.

For this reason, Muslims and others objected to those speculative theologians who said that He has power from eternity while the object of that power is impossible from eternity. They said that this combines two contradictories. They also said that it entails the object of power passing from possibility to impossibility without any cause necessitating that transition, and entails the Lord becoming capable after not having been capable, without any cause necessitating this. This matter has been discussed at length elsewhere.