to have all those ideas in our understandings, which, though we do not actually contemplate, yet we can bring in sight, and make appear again, and be the objects of our thoughts, without the help of those sensible qualities which first imprinted them there.
Attention, repetition, pleasure and pain, fix ideas.§ 3. Attention and repetition help much to the fixing any ideas in the memory: pleasure and but those which naturally at first make the deepest and most lasting impression are those which are accompanied with pleasure or pain. The great business of the senses being to make us take notice of what hurts or advantages the body, it is wisely ordered by nature (as has been shown) that pain should accompany the reception of several ideas; which, supplying the place of consideration and reasoning in children, and acting quicker than consideration in grown men, makes both the old and young avoid painful objects with that haste which is necessary for their preservation; and, in both, settles in the memory a caution for the future.
Ideas fade in the memory.§ 4. Concerning the several degrees of lasting, wherewith ideas are imprinted on the memory, we may observe, that some of them have been produced in the understanding by an object affecting the senses once only, and no more than once; others, that have more than once offered themselves to the senses, have yet been little taken notice of: the mind either heedless, as in children, or otherwise employed, as in men, intent only on one thing, not setting the stamp deep into itself: and in some, where they are set on with care and repeated impressions, either through the temper of the body, or some other fault, the memory is very weak. In all these cases, ideas in the mind quickly fade, and often vanish quite out of the understanding, leaving no more footsteps or remaining characters of themselves than shadows do flying over fields of corn; and the mind is as void of them as if they had never been there.
