Once again, transparency is not an absolute value. One good aspect of inductive teaching of grammar, for example, is the fun of working one's way out of a temporary structural fog.
Needless to say, opacity is to be calculated from the point of view of the learner. If the writer or adapter knows the language too well, he may forget that what seems obvious to him may be perplexing for students from a very different language background. On the other hand, writers sometimes spend much effort in elaborate explanation of a point that really causes the students no trouble.
Summary comments on the three qualities
The differences among the three qualities may perhaps be clarified by looking at the following sentences:
Obviously, in even the best of lessons some lines will be stronger than others, every line has some heaviness, and many
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