It is made up of five elements.  Each element making up the idea comes from one of the senses, and of these there are at present five.  Later on every idea will be a heptad, made up of seven elements.  For the present, each has five qualities, which build up the idea.  The mind unites the whole together into a single thought, synthesises the five sensations.  If you think of an orange and analyse your thought of an orange, you will find in it:  colour, which comes through the eye; fragrance, which comes through the nose; taste, which comes through the tongue; roughness or smoothness, which comes through the sense of touch; and you would hear musical notes made by the vibrations of the molecules, coming through the sense of hearing, were it keener.  If you had a perfect sense of hearing. you would hear the sound of the orange also, for wherever there is vibration there is sound.  All this, synthesised by the mind into one idea, is an orange.  That is the root reason for the “association of ideas”.  It is not only that a fragrance recalls the scene and the circumstances under which the fragrance was observed, but because every impression is made through all the five senses and, therefore, when one is stimulated, the others are recalled.  The mind is like a prism.  If you put a prism in the path of a ray of white light, it will break it up into its seven constituent rays and seven colours will appear.  Put another prism in the path of these seven rays, and as they pass through the prism, the process is reversed and the seven become one white light.  The mind is like the second prism.  It takes in the five sensations that enter through the senses, and combines them into a single precept.  As at the present stage of evolution the senses are five only, it unites the five sensations into one idea.  What the white ray is to the seven- coloured light, that a thought or idea is to the fivefold sensation.  That is the meaning of the much controverted Sutra:  “Vrittayah panchatayych,” “the vrittis, or modes of the mind, are pentads.”  If you look at it in that way, the later teachings will be more clearly understood.

As I have already said, that sentence, that nothing exists in thought which is not in sensation, is not the whole truth.  Manas, the sixth sense, adds to the sensations its own pure elemental nature.  What is that nature that you find thus added?  It is the establishment of a relation, that is really what the mind adds.  All thinking is the “establishment of relations,” and the more closely you look into that phrase, the more you will realise how it covers all the varied processes of the mind.  The very first process of the mind is to become aware of an outside world.  However dimly at first, we become aware of something outside ourselves—­a process generally called perception.  I use the more general term “establishing a relation,” because that runs through the whole of the mental processes, whereas perception is only a single thing.