3. The various degrees of attention in thinking.
But perhaps it may not be an unpardonable digression, nor wholly
impertinent to our present design, if we reflect here upon the different state of the mind in thinking, which those
instances of attention, reverie, and dreaming, etc., before mentioned, naturally enough suggest. That there are
ideas, some or other, always present in the mind of a waking man, every one's experience convinces him; though
the mind employs itself about them with several degrees of attention. Sometimes the mind fixes itself with so
much earnestness on the contemplation of some objects, that it turns their ideas on all sides; marks their relations
and circumstances; and views every part so nicely and with such intention, that it shuts out all other thoughts, and
takes no notice of the ordinary impressions made then on the senses, which at another season would produce very
sensible perceptions: at other times it barely observes the train of ideas that succeed in the understanding, without
directing and pursuing any of them: and at other times it lets them pass almost quite unregarded, as faint shadows
that make no impression.