ما معنى إثبات الشيء ضد لنفيه؟

If we affirm something for one of two matters, we automatically negate its opposite. For example, affirming life for a person negates death for them, and affirming existence and eternality for Allah negates non-existence and createdness for Him. This is what Sheikh Al-Islam Ibn Taymiyyah established: that the affirmation of one of two opposites necessitates the negation of the other.