real world situations. In the phrase of the mathematician Paul
Halmos (1980), problem solving is "the heart of mathematics".
However, whilst teachers around the world have considerable successes
with achieving this goal, especially with more able students,
there is always a great need for improvement, so that more students
get a deeper appreciation of what it means to think mathematically
and to use mathematics to help in their daily and working lives.
25
The second focus is on the conceptual development of mathematics.
Freudenthal [1973] used the word "mathematization" for
considering the process to objectify mathematical activity. What is
interesting for researchers is that he said that Polya did not explain
mathematical activity. Tall described the conceptual development
with the word "procept," and also described the three mental worlds
of embodiment, symbolism, and formalism [Tall and Isoda, to
appear]. His map of mathematical thinking, in Figure 10, shows us
one bird's-eye view.
These two perspectives of mathematical thinking explain the
complex thinking in each thinking process in mathematics in simple
terms. Making clear those terms is necessary in orders to know
what mathematical thinking is. Each of them shows a kind of denotative
description of mathematical thinking.
Additionally, in the last twenty years, there have been curricular
reform movements that were focused on competency. New terms
are used that are related to mathematical thinking. "Disposition"
is one of the words that are well known [Kilpatrick et al., 2001]. It
is deeply related to knowing the value of mathematics and the
mindset for mathematics.
These major trends in the mathematical process, conceptual
development, and dispositions are deeply related to Katagiri's thoughts
about mathematical ways of thinking, ideas, and attitude, which will
be explained in Part I. As in mathematics education research, it is necessary
to clarify the relationships between those key terms, which were
explained by Katagiri himself in his previous books written in
Japanese in the 1980s. Part I presents just the essence of his theory.
At the same time, his view of mathematical thinking will still be considered
innovative in mathematics education research, because it is
well related to the current ideas about mathematical thinking which
have been used in the major research, articles on mathematics education
as an academic discipline and, now, lesson study is developing a
new research context which recognizes the theory of mathematics education
as with reproductive science in classrooms in various settings.
In this introductory chapter, the Problem Solving Approach is
only explained briefly, in order to understand Katagiri's work in
Parts I and II. The details of the approach will be further explained
with a number of evidences of lesson study in further monographs
in this series.