Tractatus de Intellectus Emendatione (TIE) or On the Improvement of the Understanding is an attempt to formulate a philosophical method that would allow the mind to form the clear and distinct ideas that are necessary for its perfection. It contains, in addition, reflection upon the various kinds of knowledge, an extended treatment of definition, and a lengthy analysis of the nature and causes of doubt. The characteristic of the work is the discussion of different form of perception at Chapter IV and illustration of the best one in relation with the experience and intelligence at the next Chapter. He also addresses the issues of memory and forgetting.