In this and the following volumes I wish to publish a selection of the philosophical remarks which I have written down in the course of the last nine years. They concern many topics of philosophical speculation: the concepts of ‘meaning’, ‘understanding’, ‘proposition’, ‘logic’, the foundations of mathematics, sensedata, the conflict between realism and idealism, and others. All these thoughts were originally written down in the form of remarks (short paragraphs) sometimes forming connected series on the same subject, sometimes shifting rapidly from one subject to another. My intention was – some day to bring them all together in a book; regarding the form of this book I had various ideas at different times. It seemed essential however that the thoughts in it should pass from one subject to another in an ordered sequence.