5.541 At first glance it seems as though there is another way in which a proposition can occur in another.
Especially in certain propositional forms of psychology, like “A believes that p is the case”, or “A thinks p”, etc.
Here it seems superficially as though the proposition p stands in a kind of relation to an object A.
(And in the modern theory of knowledge (Russell,
According to Russell, when you have a sentence like ‘A believes p’, p cannot stand for a fact, since then you could only ever have true beliefs. Nor can p be a proposition, since propositions do not really exist. What you believe cannot be a logical fiction, but must be something real. So how can we have false beliefs? How can we really believe something that is not the case? For instance, in ‘A believes Hamlet lives in Finland’ we cannot relate A to a proposition and ‘lives in’ must be treated as a verb, even though Hamlet does not live in Finland and there is no non-existent Hamlet who does so, nor a non-existent Finland in which he lives. Russell does not know how to solve this problem, at least not in Logical Atomism. Earlier, in Theory of Knowledge, he treated propositions as functions of judgments, consisting of objects that the person making the judgment is acquainted with. These objects include relations. But then the relation becomes just another object, so how is it to be related to the other objects, and how are they to be related to it? We cannot simply assume that the objects are related correctly in the judgment, since people judge falsely sometimes. These are the problems that Wittgenstein appears to have pointed out to Russell, and that he wrestles with in Logical Atomism. Contrast Frege’s view that in the proposition ‘Copernicus thought that the planetary orbits are circular’ “the man and the thought occupy, so to speak, the same stage.” I.e., Frege takes this sentence to relate two objects, a man (Copernicus) and a thought (that the planetary orbits are circular).
 Frege Philosophical and Mathematical Correspondence ed. Brian McGuinness, trans. Hans Kaal, University of Chicago Press, 1980, p. 164.