It means that though the Witch knew the Deep Magic, there is a magic deeper still that she did not know. Her knowledge goes back only to the dawn of Time. But if she could have looked a little further back, into the stillness and darkness before Time began, she would have read there a different incantation. She would have known that when a willing victim who had committed no treachery was killed in a traitor's stead, the Table would crack and death itself would work backwards.
C. S. LewisThe human mind is generally far more eager to praise and dispraise than to describe and define. It wants to make every distinction a distinction of value; hence those fatal critics who can never point out the differing quality of two poets without putting them in an order of preference as if they were candidates for a prize.
C. S. Lewis