Some features of causal reasoning: common sense and physics teaching

Abstract

The idea of causality is central in science and has long given rise to debate among philosophers and scientists. While the tendency to avoid causality seems to have become dominant in science and philosophy, research in science education has shown the strong presence in common reasoning of causal explanations, often conceived as a ‘mechanism’ capable of accounting for physical transformations. Some researchers have proposed using this common causal reasoning as a basis for teaching–learning sequences, especially in electricity and mechanics. This paper analyses some features of causal reasoning used in physics by students, using questionnaires and interviews involving students and teachers. This study has shown three aspects which are related to one another: a confusion between efficient and contingent causes, between the conditions of occurrence of a phenomenon and the cause actually producing it; a tendency to ‘displace’ causes, skipping intermediate objects; and a difficulty in connecting local causes and global effects. The paper highlights the differences between common reasoning and scientific usage, and their effect on learning. In fact, these trends of reasoning must be taken into account in teaching: they should be considered not only as creating an obstacle to learning physics, but also as resources at the learner’s disposal.

Notes

Laboratoire de Didactique des Sciences Physiques, Université de Paris 7 ‘Denis Diderot’, Case 7086, 2 place Jussieu, 75251 Paris Cedex 05, France. Email: [email protected]

‘ “Realism” is… “A doctrine according to which being is independent of the knowledge that conscious subjects may have of it at a given time: esse is not equivalent to percepi.” Idealists hold that the intellect knows only its own states: see the commentaries on contemporary physics, which deny the existence of any given external to our representations (to measurements made by observers). Realism and idealism are opposed term for term, each asserting what the other denies. The first posits that thought is in the being; the second posits that the being is contained in thought’ (Largeault, 2002).

Many students think that no horizontal forces act on the upper block, whose movement is explained without force, by the idea of ‘drag’ or ‘adherence’ between blocks (Caldas & Saltiel, 1995; Besson, 1996). In a similar situation (on a table, a sheet of paper is placed under a book and it moves when the book is moved), Di Sessa (1998, pp. 1181–1182) found that the student interviewed did not think that a force is necessary to account for the moving paper, because ‘it [the book] is just taking the paper with it’. Di Sessa interpreted this as an example of a specific primitive cognitive structure (p‐prim), contact conveys motion, which negates the need for a force.

Additional information

Notes on contributors

Ugo Besson

Laboratoire de Didactique des Sciences Physiques, Université de Paris 7 ‘Denis Diderot’, Case 7086, 2 place Jussieu, 75251 Paris Cedex 05, France. Email: [email protected]