Thoughts are things
Dreams, What they are and how they are caused
'thoughts are things', for every thought impresses itself upon the plastic elemental essence and generates a temporary living entity, the duration of whose life depends upon the energy of the thought-impulse given to it. We are therefore living in the midst of an ocean of other men's thoughts, and whether we are awake or asleep, these are constantly presenting themselves to the etheric part of our brain.
64. So long as we ourselves are actively thinking and therefore keeping our brain fully employed, it is practically impervious to this continual impingement of thought from without; but the moment that we leave it idle, the stream of inconsequent chaos begins to pour through it. Most of the thoughts sweep through unassimilated and almost unnoticed, but now and then one comes along which reawakens some vibrations to which the etheric part of the brain is accustomed; at once that brain seizes upon it, intensifies it, and makes it its own; that thought in turn suggests another; and so a whole train of ideas is started, until eventually it also fades away, and the disconnected, purposeless stream begins flowing through the brain again.
65. The vast majority of people, if they will watch closely what they are in the habit of calling their thoughts will find that they are very largely made up of a casual stream of this sort — that in truth they are not their thoughts at all, but simply the cast-off fragments of other people's. For, the ordinary man seems to have no control whatever over his mind; he hardly ever knows exactly of what he is thinking at any particular moment, or why is he thinking of it; instead of directing his mind to some definite point, he allows it to run riot at its own sweet will, or lets it lie fallow, so that any casual seed cast into it by the wind may germinate and come to fruition there.
66. The result of this is that even when he, the ego, really wishes for once to think consecutively on any particular subject, he finds himself practically unable to do so; all sorts of stray thoughts rush in unbidden from every side, and since he is quite unused to controlling his mind, he is powerless to stem the torrent. Such a person does not know what real concentrated thought is; and it is this utter lack of concentration, this feebleness of mind and will, that makes the early stages of occult development so difficult to the average man. Again, since in the present state of the world's evolution there are likely to be more evil thoughts than good ones floating around him, this weakness lays him open to all sorts of temptations which a little care and effort might have avoided altogether.