28. Many pupils reveal a curious contrast. In their own sphere they display a good memory, a lively imagination, keen understanding; by the teacher they are credited with little of all these. They rule perhaps over their playmates because of their superior intelligence, or possess at least the respect of the latter, while in their classes they show only incapacity. Such experiences suggest the difficulty of making instruction take proper hold of the inner growth of the pupil. It is evident, at the same time, that what is customarily ascribed to the action of the various mental faculties takes place in certain groups of ideas. 29. The grown man has one group of ideas for his church, another for his work at home, a third for society, and so on. These groups, though partially interacting and mutually determinant, are far from being connected at every point. This is true as early as boyhood. The boy has one set of ideas for his school, another for the family circle, still another for the playground, etc. This fact explains better than intentional reserve the observation that a boy is one being at home or at school and quite another among strangers. 30. Each body of ideas is made up of complications of ideas, which, if the union is perfect, come and go in consciousness as undivided wholes, and of series, together with their interlacings, whose members unfold successively, one by one, provided they are not checked. The closer the union of parts within these complications and series, the more absolute the laws according to which ideas act in consciousness, the stronger is the resistance against everything opposing their movement; hence the difficulty of acting upon them through instruction. They admit, however, of additions and recombinations, and so may in the course of time undergo essential changes; up to a certain point they even change of themselves if repeatedly called into consciousness by dissimilar occasions, _e.g._, by the frequent delivery of the same lecture before different audiences. The general notions of things are complexes or complications of their attributes. Other examples of complexes important to instruction are furnished by logical concepts and words. But since words of several languages may be perfectly complicated or bound together with the same concept, without being just as intimately connected with one another, it should be noted that when the object or concept comes up at different times, it will be joined now with this and next with another language. Yet the repeated perception of the object is not quite the same perception as before, although earlier ideas mostly coalesce so fully with later homogeneous ideas that the difference makes itself felt but little.