Knowledge cannot be passed, like some material substance…

““Knowledge cannot be passed, like some material substance, from one person to another. Thoughts are not things which may be held and handled. They are the unseen and silent acts of the invisible mind. Ideas, the products of thought, can only be communicated by inducing in the receiving mind action correspondent to that by which these ideas were first conceived. In other words, ideas can only be transmitted by being rethought. It is obvious, therefore, that something more is required than a passive presentation of the pupil’s mind to the teacher’s mind as face turns to face. The pupil must think. His mind must work, not in a vague way, without object or direction, but under the control of the will, and with a fixed aim and purpose; in other words, with attention. It is not enough to look and listen. The learner’s mind must work through the senses. There must be mind in the eye, in the ear, in the hand. If the mental power is only half aroused and feeble in its action, the conceptions gained will be faint and fragmentary, and the knowledge acquired will be as inaccurate and useless as it will be fleeting. Teacher and text-book may be full of knowledge, but the learner will get from them only so much as his power of attention, vigorously exercised, enables him to shape in his own mind. Knowledge is inseparable from the act of knowing. If the power of knowing is small, the actual knowledge acquired will also be small.””

— John M Gregory