Please excuse this letter as springing from my unsatisfied need for communication.  I find myself in a vicious circle:  before people pay attention to my Begriffsschrift, they want to see what it can do, and I in turn cannot show this without presupposing familiarity with it.  So it seems I can hardly count on any readers for the book I mentioned…  (Letter to Marty)

This book will perhaps only be understood by those who have themselves already thought the thoughts which are expressed in it–or similar thoughts.   It is therefore not a text-book.  (Preface to TLP)