ABSTRACT
When the science of psychology attempts to explain mental development, it must of necessity deal with each aspect of this development separately. When, for example, the processes are under consideration by which motor skills are acquired, it is impossible to discuss at the same time the development of number ideas. When the complexities of reading are being described, it would be distracting to introduce an account of the way in which the products of the fine arts are appreciated. The separate consideration of the different aspects of mental development for purposes of scientific study would be seriously misleading, however, if it gave rise to the view that mental life is made up of unrelated compartments. The fact is that skill and number ideas have been combined in human experience and their union has produced mechanical precision, a higher achievement than would have been possible without the combination of two different phases or aspects of mental life. The fine arts have been perfected not only through refinements of art products but also through the recording of critical judgments and the presentation of illuminating suggestions in written and printed documents that are read. Mental abilities, however different their origins and their development, are phases of an inclusive whole within which they are interrelated, each making its contribution to the unity which is described by such terms as “intelligence,” “individual experience,” and “personality.” It is important, therefore, after the various special mental abilities have been canvassed separately, as they are in Part Two of this book, to give consideration to the fact that mental life has a certain totality and unity which is more than the mere sum of its different aspects.
