(another personal favourite)" A combination composed of a sacrifice has more immediate effect upon the person playing over the game in which it occurs than another combination, because the apparent senselessness of the sacrifice is convincing proof of the design of the player offering it.
On advanced ideas:
"After giving a student the basic mating patterns and strategies you must begin giving them advanced concepts. At first these ideas will not make sense, many players will have a vague idea of what you are talking about but nothing more. Even a fragmented understanding of these concepts will prove useful though, and eventually they will improve as these lessons are assimilated by repetition and example." Jeremy SILMAN, The Amateur's Mind, 1995
"We begin with the hypothesis that any subject can be taught effectively in some intellectually honest form to any child at any stage of development. ... (The "spiral curriculum") ... Is it not possible ... to introduce them to some of the major ... ideas earlier, in a spirit perhaps less exact and more intuitive?"Jerome BRUNER