John Locke said this quote

This is that which I think great readers are apt to be mistaken in. Those who have read of every thing are thought to understand every thing too; but it is not always so. Reading furnishes the mind only with materials of knowledge; it is thinking makes what we read ours. We are of the ruminating kind, and it is not enough to cram ourselves with a great load of collections; unless we chew them over again, they will not give us strength and nourishment.