So comprehensive is modern psychology, seeming to aim at constructing anew the entire world of thought. And prior to or simultaneously with this construction a negative process has to be carried on, a clearing away of useless abstractions which we have inherited from the past. Many erroneous conceptions of the mind derived from former philosophies have found their way into language, and we with difficulty disengage ourselves from them. Mere figures of speech have unconsciously influenced the minds of great thinkers. Also there are some distinctions, as, for example, that of the will and of the reason, and of the moral and intellectual faculties, which are carried further than is justified by experience. Any separation of things which we cannot see or exactly define, though it may be necessary, is a fertile source of error. The division of the mind into faculties or powers or virtues is too deeply rooted in language to be got rid of, but it gives a false impression. For if we reflect on ourselves we see that all our faculties easily pass into one another, and are bound together in a single mind or consciousness; but this mental unity is apt to be concealed from us by the distinctions of language. A profusion of words and ideas has obscured rather than enlightened mental science. It is hard to say how many fallacies have arisen from the representation of the mind as a box, as a 'tabula rasa,' a book, a mirror, and the like. It is remarkable how Plato in the Theaetetus, after having indulged in the figure of the waxen tablet and the decoy, afterwards discards them. The mind is also represented by another class of images, as the spring of a watch, a motive power, a breath, a stream, a succession of points or moments. As Plato remarks in the Cratylus, words expressive of motion as well as of rest are employed to describe the faculties and operations of the mind; and in these there is contained another store of fallacies. Some shadow or reflection of the body seems always to adhere to our thoughts about ourselves, and mental processes are hardly distinguished in language from bodily ones. To see or perceive are used indifferently of both; the words intuition, moral sense, common sense, the mind's eye, are figures of speech transferred from one to the other. And many other words used in early poetry or in sacred writings to express the works of mind have a materialistic sound; for old mythology was allied to sense, and the distinction of matter and mind had not as yet arisen. Thus materialism receives an illusive aid from language; and both in philosophy and religion the imaginary figure or association easily takes the place of real knowledge.