Introduction

The triangle formed by the relationship between a teacher, a learner, and the object to be learned is a common way of representing what teachers need to know when teaching their pupils. Teachers' knowledge of the content to be learned is referred to as subject matter knowledge; their knowledge of how students learn about this object, of their conceptions (or misconceptions) before they are taught and how their knowledge changes through instruction, is known as pedagogical content knowledge (Schulman 1986; Strauss et al. 1999). Schulman argued that subject-matter knowledge for teaching is more than what is expected of the subject major who is not preparing for teaching. ‘We expect the teacher to understand why a given topic is particularly central to a discipline whereas another may be somewhat peripheral. This will be important in subsequent pedagogical judgments regarding relative curricular emphasis’ (Schulman 1986: 9). Schulman proposed that pedagogical content knowledge must include knowledge of ‘the most useful forms of representation of those ideas [to be taught], the most powerful analogies, illustrations, examples, explanations, and demonstrations – in a word, the ways of representing and formulating the subject that make it comprehensible to others’ (Schulman 1986: 9). Schulman's distinction between these two forms of knowledge, and the emphasis on the connections between them, is a landmark for many who are concerned with teacher education.