One of the educational by-products of German botanical scholarship was the publication of sets of large ‘wall diagrams’ for use in the lecture-room. Most British University Departments of Botany dating from the period before the first world war probably had at least one of these sets. In my own department I have used these excellent diagrams occasionally, realizing that they combined clarity, size and accuracy to an unrivalled extent.This passage from a recent essay by S. M. Walters forms an appropriate (...) introduction to the topic of this paper. From the start, it should be noticed that the use of such diagrams was by no means limited to botany nor to university studies. As will become clear, they were one of the most important media for the teaching and learning at different levels of education and within different fields. (shrink)

An examination of footnotes, quotations, and name-lists shows that historians try to follow the reality rule - to tell about the past the most likely story that can be sustained by the relevant existing evidence. But this is modified by the maximum impact rule - stories must have evocative force, and the reader should actively confront the past. The maximum impact rule may require the historian to sacrifice some completeness and exactness for evocative impact; and there is no parallel to (...) this sacrifice in scientific explanations. History, as it is practiced, is a rule-bound discipline, with rules and a rhetoric different from those of scientific explanation. There is no need for historians to structure their explanations according to the pattern of the sciences. (shrink)