اللَّهُ خَالِقُ كُلِّ شَيْءٍ
“God is the Creator of everything.” (Qurʾān 13:16)
The expression kulli shayʾ is general. Sunni theologians include human beings and their originated acts within its scope, because an act occurring in time is also a contingent thing. The response considers whether a valid rational or textual specification can restrict this generality.
It is not enough to claim that general expressions can never admit exceptions; rather, excluding human actions requires a sound specifying reason. Simply assuming that humans are independent creators would beg the very question being argued.