Kay truly observes: "By adopting the opinion that every thought or impression that had once been consciously before the mind is ever afterwards retained, we obtain light on many obscure mental phenomena; and especially do we draw from it the conclusion of the perfectibility of the memory to an almost unlimited extent. We cannot doubt that, could we penetrate to the lowest depths of our mental nature, we should there find traces of every impression we have received, every thought we have entertained, and every act we have done through our past life, each one making its influence felt in the way of building up our present knowledge, or in guiding our every-day actions; and if they persist in the mind, might it not be possible to recall most if not all of them into consciousness when we wished to do so, if our memories or powers of recollection were what they should be?" As we have said, this great subconscious region of the mind--this Memory region--may be thought of as a great record file, with an intricate system of indexes, and office boys whose business it is to file away the records; to index them; and to find them when needed. The records record only what we have impressed upon them by the attention, the degree of depth and clearness depending entirely upon the degree of attention which we bestowed upon the original impression. We can never expect to have the office boys of the memory bring up anything that they have not been given to file away. The indexing, and cross-references are supplied by the association existing between the various impressions. The more cross-references, or associations that are connected with an idea, thought or impression that is filed away in the memory, the greater the chances of it being found readily when wanted. These two features of attention and association, and the parts they play in the phenomena of memory, are mentioned in detail in other chapters of this book.