It may be found that the same principle helps to account for the exaggerated importance which we attach to the impressions of our dreams.
It is evident that all indistinct impressions are liable to be wrongly classed.

Sensations answering to a given colour or form, are, when faint, easily confused with other sensations, and so an opening occurs for illusion.

Thus, the impressions received from distant objects are frequently misinterpreted, and, as we shall see by-and-by, it is in this region of hazy impression that imagination is wont to play its most startling pranks.
It is to be observed that the illusions arising from wrong classification will be more frequent in the case of those senses where discrimination is low.

Thus, it is much easier in a general way to confuse two sensations of smell than two sensations of colour.

Hence the great source of such errors is to be found in that mass of obscure sensation which is connected with the organic processes, as digestion, respiration, etc., together with those varying tactual and motor feelings, which result from what is called the subjective stimulation of the tactual nerves, and from changes in the position and condition of the muscles.