It is not the intention of this introduction to psy-chology to discuss the scientific or philosophical conceptions of psychology, or even to make a survey of the investigations and their results. What this little book attempts is rather to introduce the reader to the principal thoughts underlying present day experimental psychology, leaving out many facts and methods which would be necessary for a thorough study of the subject. To omit all mention of experimental methods and their results is at the present day impossible. Yet we only need to consider a comparatively small number of results of the first importance in order to comprehend the basic principles of the new psychology. To characterise the methods of this psychology it would be impossible to omit all reference to experiments, but we can and will omit reference to the more or less complicated instruments on which the carrying out of such experiments de-pends. I must refer the reader who wishes a Psychology, which also contains the necessary bibliography of the subject.