This final chapter deals with two separate developments in Russell's thought in the period 1906-13. One concerns fundamental metaphysical issues. Here Russell's views undergo a definite change: the notion of truth, and of a proposition, are displaced from their central metaphysical role, which is increasingly occupied by the notion of a fact. For reasons which are not immediately obvious, but will emerge, Russell's adoption of what he calls 'the multiple relation theory of judgment' is intrinsic to this change. The second development is, I think, not a change of doctrine on Russell's part but rather a shift of interest. He comes to be increasingly concerned with the question of knowledge: how, and to what extent, we can know the things that we take ourselves to know. The emphasis here is not on our (putative) knowledge of logic and mathematics, but rather on our knowledge of the physical world—from humble statements about there being a table in front of me to the most esoteric assertions of physics. Both of these developments of Russell's thought give rise to much subsequent work. My purpose in this chapter is not to give a full account of his thought on these matters but to indicate the main lines of the developments that I have mentioned, and especially their relation to Russell's earlier work.
The two developments mentioned above are distinct and I shall discuss them separately. There are, however, two themes which connect them. The first is quite general, and of great significance from our point of view. It is in the two developments which are the subject of this chapter that one begins to see the emergence of what we might call 'constructionalism' as a general method in philosophy. The general idea of constructionalism is of course familiar from the project of reducing mathematics to logic (or constructing mathematics from logic). In the two developments discussed in this chapter, most obviously in the second, we see something new: constructionalism becomes a general philosophical method. This method came to be an important strand running through the tradition of analytic philosophy;