will be partly opaque. Furthermore, the three criteria will often conflict with one another: a line may be very strong but also heavy, or transparent but also weak. Even so, they may be worth the attention of anyone who is writing or evaluating language lessons. Lightness and transparency can conceivably be made permanent attributes of permanent lessons, but only constant adaptation will keep strength from deteriorating.
EVALUATION: THREE DIMENSIONS
The content of a textbook, or a lesson, or a drill, or a single line may be plotted in each of three dimensions: linguistic, social and topical.
The linguistic dimension. ('How well must they speak?)
In a course as a whole, the linguistic content that is needed is relatively independent of the age, occupation or special interests of the prospective students. This content consists mainly of phonological patterns and structural devices. Because this aspect of content is so dependable, text writers have too often accorded the linguistic dimension absolute primacy: Social and topical content need not be absorbing, but only plausible and appropriate for illustrating a series of linguistic points. This is particularly likely to happen when the materials developer is also a trained linguist, intent on sharing with the readers his enjoyment of the intricacies and symmetries of linguistic structure. Even before the ascendancy of linguistic science, of course, one type of textbook subordinated everything else to the purpose of conveying patterns. (That must surely have been the purpose behind 'Your horse had been old.') But in the absence of resolute and meticulous planning for other sources of reward, strength is drawn
50
