Full Idea
The memory contains the innumerable principles and laws of numbers and dimensions. None of these can have been conveyed to me by the bodily senses.
Gist of Idea
Memory contains innumerable principles of maths, as well as past sense experiences
Source
Augustine (Confessions [c.398], X.12)
A Reaction
Even if you have a fairly empirical view of the sources of mathematics (a view with which I sympathise), it must by admitted that our endless extrapolations from the sources also reside in memory. So we remember thoughts as well as experiences.
Book Reference
Augustine: 'Confessions', ed/tr. Pine-Coffin,R.S. [Penguin 1961], p.219