How did Keynes transform his theory from the Tract into the Treatise ?—Consideration through primary material

The main purpose of this paper is to clarify on the evidence of primary material how Keynes transformed his theory from the Tract to the Treatise. Keynes went on working along the lines of the Tract theory until around April 1926, subsequently adopting the Transaction Approach up until September 1927. The paper stresses the importance of the three TOC between September 1927 and September 1928 as pointing the way towards the Treatise's fundamental equations - the breakthrough opening the way to the Treatise. The second fundamental equation, the TM supply function and the natural rate of interest had made their appearance by April 1930.