The thoughts that I publish in what follows are the precipitate of philosophical investigations which have occupied me for the last sixteen years. They concern many subjects: the concepts of meaning, of understanding, of a proposition and sentence, of logic, the foundations of mathematics, states of consciousness, and other things. I have written down all these thoughts as remarks, short paragraphs, sometimes in longer chains about the same subject, sometimes jumping, in a sudden change, from one area to another. -- Originally it was my intention to bring all this together in a book whose form I thought of differently at different times. But it seemed to me essential that in the book the thoughts should proceed from one subject to another in natural, smooth sequence.
After several unsuccessful attempts to weld my results together into such a whole, I realized that I should never succeed. The best that I could write would never be more than philosophical remarks; my thoughts soon grew feeble if I tried to force them along a single track against their natural inclination. --- And this was, of course, connected with the very nature of the investigation. For it compels us to travel criss-cross in every direction over a wide field of thought. -- The philosophical remarks in this book are, as it were, a number of sketches of landscapes which were made in the course of these long and meandering journeys.