First and most useful generally are general intelligence tests, which must usually be subdivided into a series of related tests. Then, for varying purposes, such as the examination of candidates for particular classes of employment requiring special ability or capacity, there may be applied speed tests, accuracy tests, perception tests, coördination tests, memory tests, mathematical tests, and a wide variety of others. These are tests which primarily measure the subject’s ability to perform certain specific acts under pre-determined conditions, the determination of capacity in excess of that actually demonstrated under test depending upon the facility and accuracy with which the subject responds to the conditions of these tests. Of course, every scientific mental test is based upon the performance of certain acts, since it is only through action of some sort, whether by speech, writing, or the performance of a manual operation, that any one is able to express his mental ability at any time. But while it is relatively a simple matter to devise tests that satisfactorily indicate the subject’s possession of the more obvious mental powers indicated by such tests as those last listed above, there is another class of mental tests, designed primarily to indicate or determine the possession of the more abstract qualities, the manifestation of which through the individual’s simple and ordinary actions is less obvious to the untrained observer. This is the class of tests that are designed to measure the degree in which an individual possesses such qualities as moral sense, form perception, the power to reason from cause to effect, poetic discrimination, ability to understand complicated instructions, judgment, sense of the right relationship of things and ideas. It is as important, if one is to arrive at a true measure of any individual’s mental capacity, that he be tested as to his possession of these more or less abstract qualities, as it is to determine his possession of concrete abilities. In other words, the normal mind of an intelligent adult is capable of dealing intelligently with ideas and abstractions. The mentality that does not respond with a certain degree of readiness to ideal conceptions is to that extent sub-normal. The only possible way of determining the possession of unusual or super-normal mental capacity is by means of the demonstration that its possessor grasps readily and responds unhesitatingly to the presentation of abstract concepts. The demonstration itself must, of course, be concrete. Unless the individual possessing extraordinary mental power is able, as Kipling phrases it, to . . . . press the logic of a fact To its ultimate conclusion in unmitigated act. it is of no social consequence whatever that he may possess the mental catholicity of a Shakespeare. There is no place in the modern world for “mute, inglorious Miltons.”