These works, as the sub-title makes clear, are unfinished sketches for
Philosophical Investigations, possibly the most important and influential
philosophical work of modern times. The 'Blue Book' is a set of notes
dictated to Witgenstein's Cambridge students in 1933-1934: the 'Brown Book'
was a draft for what eventually became the growth of the first part of
Philosophical Investigations. This book reveals the germination and growth
of the ideas which found their final expression in Witgenstein's later
work. It is indispensable therefore to students of Witgenstein's thought
and to all those who wish to study at first-hand the mental processes of a
thinker who fundamentally changed the course of modern philosophy.