Hans Freudenthal: Other

“[The goal of developmental research is to] consciously experience, describe and justify the cyclic process of development and research so that it can be passed on to others in such a way that they can witness and relive the experience.”

Hans Freudenthal

Freudenthal (1988) "Ontwikkelingsonderzoek"; As cited Els Feijs (2005) Constructing a Learning Environment that Promotes Reinvention

Way

“While studying antiaircraft fire control, Wiener may have conceived the idea of considering the operator as part of the steering mechanism and of applying to him such notions as feedback and stability, which had been devised for mechanical systems and electrical circuits. No doubt this kind of analogy had been operative in Wiener’s mathematical work from the beginning and sometimes had even been productive. As time passed, such flashes of insight were more consciously put to use in a sort of biological research for which Wiener consulted all kinds of people, except mathematicians, whether or not they had anything to do with it. Cybernetics, or Control and Communication in the Animal and the Machine (1948) is a rather eloquent report of these abortive attempts, in the sense that it shows there is not much to be reported. The value and influence of Cybernetics, and other publications of this kind, should not, however, be belittled. It has contributed to popularizing a way of thinking in communication theory terms, such as feedback, information, control, input, output, stability, homeostasis, prediction, and filtering. On the other hand, it also has contributed to spreading mistaken ideas of what mathematics really means”

Hans Freudenthal

Norbert Wiener (2008)

People , Way , Communication , Mathematics

“The subject of a science is never well circumscribed and there is little use sharpening its definition. However, nobody will deny that physics deals with nature and sociology with human society in some of their aspects. With logic, it is another matter. Logic is usually understood nowadays as a study of certain formal systems, though in former times there were philosophers who held that the subject matter of logic was the formal rules of human thought. In the latter sense it would be an empirical rather than a formal science, though its empirical subject matter would still be fundamentally different from that of psychology of thinking. One interpretation of logic does not exclude the other. Formal approaches are often easier than empirical ones, and for this reason one can understand why logic as a study of formal systems has till now made more progress than logic as a study of the formal rules of thought, even if restricted to scientific thought.”

Hans Freudenthal

Source: Realistic models in probability (1968), p. 1

Understanding , Nature , Thinking , Sense

“No scientist is as model minded as is the statistician; in no other branch of science is the word model as often and consciously used as in statistics.”

Hans Freudenthal

Source: The Concept and the Role of the Model in Mathematics and Natural and Social Sciences (1961), p. 79; Part of the article "Models in applied probability", published earlier in Synthese, 12 (1960), p. 204-210.

Science

“Euclid defines the angle as an inclination of lines…he meant halflines, because otherwise he would not be able to distinguish adjacent angles from each other… Euclid does not know zero angles, nor straight and bigger than straight angles…Euclid takes the liberty of adding angles beyond two and even four right angles; the result cannot be angles according to the original definitions…Nevertheless one feels that Euclid’s angle concept is consistent.”

Hans Freudenthal

Source: Mathematics as an Educational Task (1973), p. 476-477

Feeling

“Angles are measured by arcs, such that 360° and 2π correspond to each other.”

Hans Freudenthal

Source: Mathematics as an Educational Task (1973), p. 477

“Grasping spatial gestalts as figures is mathematizing of space. Arranging the properties of a parallelogram such that a particular one pops up to base the others on it in order to arrive at a definition of parallelogram, that is mathematizing the conceptual field of the parallelogram.”

Hans Freudenthal

Source: Mathematics as an Educational Task (1973), p. 133

Mathematics

“The classic instrument to measure drawn angles and to draw angles of a given measure is the protractor — essentially half a circular ring, subdivided by ray segments into 180 degrees. For reasons I was unable to find out, this instrument has recently been superseded by an isosceles right triangle — called geo-triangle, solid, transparant, made of plastic — with an angular division radiating from the midpoint of the hypotenuse to the other sides. Well, inside the triangle half a circle with the midpoint of the hypotenuse as its centre is indicated, and from the position of the degree numbers it becomes clear that it is the semicircle that really matters. One is inclined to say "an outrageously misleading instrument"…”

Hans Freudenthal

Source: Mathematics as an Educational Task (1973), p. 363

Drawing