  We have seen how Russell's adherence to the Acquaintance Principle together with his adoption of a Fregean attitude towards misidentification led him to deny that we can think directly about extra-mental particulars. Russell admitted that there is an extra-mental reality filled with extra-mental particulars that we can and do think about. Like Frege, all such thought, Russell insisted, is indirect. But Russell did not follow Frege in introducing senses as the mediators between individuals and our thought about them. Rather, Russell appealed to logical analysis through his theory of descriptions. For Russell, all thought about extra-mental particulars is descriptive. In (1910), the canonical form such thought took is the following: The thing that caused THIS [demonstratively referring to one's occurrent sense datum] is such-and-such, which is singular with respect to the sense datum demonstrated. We can work up to this by seeing how Russell contrasted three thoughts about Bismarck to the effect that he unified Germany (1910, 114–17). First, assuming acquaintance with the self, there is Bismarck's own thought about himself. This thought is singular with respect to Bismarck, having as its content the singular proposition [Bismarck unified Germany]. “But if a person who knew Bismarck made a judgment about him, the case is different. What this person was acquainted with were certain sense data which he connected (rightly, we will suppose) with Bismarck's body” (114). No human but Bismarck, then, can grasp this singular proposition. Someone that has perceived Bismarck, say, Wilhelm II, has a thought with the following form, where BOB is the sense datum the agent has in virtue of his perception of Bismarck.