In June of 1929 Wittgenstein was awarded a Ph.D. from Cambridge University, having returned to England, and to philosophy, less than a year earlier. His examiners were Russell and Moore, and for his dissertation he had submitted his Tractatus, published some seven or eight years earlier, written earlier than that, and now famous. The following month, he refused to read a paper (“Some Remarks on Logical Form”) which he had prepared for the joint session of the Mind Association and Aristotelian Society, and which obviously goes with the ideas he had worked out in the Tractatus. Years later he said to Moore “something to the effect that, when he wrote [the paper on logical form] he was getting new ideas about which he was still confused, and that he did not think it deserved any attention.”

In January of 1930 he began lecturing at Cambridge about those new ideas, and in the academic session of 1933–1934 he dictated a set of notes in conjunction with his lectures; during 1934–1935 he dictated privately another manuscript, longer than the former, more continuously evolving and much closer in style to the Philosophical Investigations.