In the course of editing this volume I discovered that I am temper amentally unsuited to the task, an impediment that in no small way accounts for the fact that its publication is later than I would have hoped or anticipated. I am, at heart, a pedant, particularly with respect to the use and abuse of the English language. Many of my scientific colleagues are a good deal less punctilious; they take the reasonable view that if the message is clear, the manner of expression is unimportant. Experience has taught me that what is clear to the author is often quite unclear to the reader unless the author takes the trouble to express himself with precision. I have also found that most scientists are unwilling to devote to the presentation of their results the care that they lavish on obtaining them. But I found myself slipping beyong this often justifiable complaint into a state of inexcusable self-righteousness. It began innocently enough. Conscious of the need for speed, I read the first two or three texts with murmurs of approval, and scribbled ‘no changes needed’ on the title page of the copy. Then I began to notice one or two grammatical mistakes, plural verbs with singular nouns, mixtures of tenses, and so on, which had to be corrected; not serious, I told myself, a matter only of changing a word here, retyping a line there. Quickly I sank deeper.