The chief characteristic of ordinary thinking is that each single act of thinking injures the nervous system, and above all, the brain; it destroys something in the brain. Every thought means that a minute process of destruction takes place in the cells of the brain. For this reason sleep is necessary for us, in order that this process of destruction may be made good; during sleep we restore what during the day was destroyed in our nervous system by thinking. What we are consciously aware of in an ordinary thought is in reality the process of destruction that is taking place in our nervous system.
We now endeavour to practise meditation by devoting ourselves to contemplation, for instance, of the saying: Wisdom lives in the Light. This idea cannot originate from sense-impressions because according to the external senses it is not so.
In this example, by means of meditation we hold the thought back so far that it does not connect itself with the brain. If in this way we unfold an inner activity of thinking that is not connected with the brain, through the effects of such meditation upon the soul we shall feel that we are on the right path. As in meditative thinking no process of destruction is evoked in our nervous system, this kind of thinking never causes sleepiness, however long it may be continued, as ordinary thinking may easily do.
It is true that the opposite often occurs when someone is meditating, for people often complain that when they devote themselves to meditation they at once fall asleep. But that is because the meditation is not yet as it should be. It is quite natural that in meditation we should, to begin with, use the kind of thinking to which we have always been accustomed; it is only gradually that we can accustom ourselves to give up thinking about external things. When this point is reached meditative thinking will no longer make us sleepy, and we shall then know that we are on the right path.
Source: Rudolf Steiner – GA 152 – Occult Science and Occult Development: Lecture 1 – London, 1st May 1913
Translated by Dorothy S. Osmond