The first that must exist with that who wants to experience a practical development of thinking is that he confides in reality, in the reality of thoughts. What does this mean? You cannot scoop water from a glass without water. You cannot take out thoughts from a world without thoughts. It is absurd if one believes that the whole sum of our thoughts and mental pictures exists only in us.
If anybody disassembles a clock and reflects the principles of its construction, then he must suppose that the watchmaker has joined the parts of the clock first according to these principles. Nobody should believe that one could find any thought from a world, which is not created and formed according to thoughts. All that we learn about nature and its events is nothing else than what must be put first into this nature and its events. It is no thought in our soul, which has not been outdoors in the world first. Aristotle said more correctly than some modern people did: what the human being finds in his thinking last exists in the world outdoors first.
However, if anybody has this confidence in the thoughts, which are contained in the world, then he sees very easily that he has to educate himself at first to a thinking full of interest in the world.
Source: Rudolf Steiner – GA 57 – The Practical Development of Thinking – Berlin, 11th February, 1909