I'm new to philosophy and have picked up Bertrand Russell's 'The Problems of Philosophy'. I have a question relating to the end of the chapter on 'Acquaintance and Description'. Russell states that we can make no judgements concerning a man, identified by the description of 'the most long-lived of men', which involve knowledge beyond what the description gives. Why can't the same be said about 'the first Chancellor of the German Empire'? We can only make the judgement that he 'was an astute diplomatist' based on something with which we are acquainted, outside of the original description. Conversely, if we knew that 'the most long-lived of men' was sufficient to identify a man about whom we knew a lot more based on things we were acquainted with, would it be wrong to state a judgement involving this extra knowledge?
Here is the relevant passage from Russell's Problems of Philosophy:"It will be seen that there are various stages in the removal from acquaintance with particulars: there is Bismarck to people who knew him; Bismarck to those who only know of him through history; the man with the iron mask; the longest-lived of men. These are progressively further removed from acquaintance with particulars; the first comes as near to acquaintance as is possible in regard to another person; in the second, we shall still be said to know 'who Bismarck was'; in the third, we do not know who was the man with the iron mask, though we can know many propositions about him which are not logically deducible from the fact that he wore an iron mask; in the fourth, finally, we know nothing beyond what is logically deducible from the definition of the man".
Russell gives examples in which he assumes various degrees of external (outside of the description) knowledge about the objects described, more or less based on colloquial understanding of these descriptions. If we change the assumptions on this score then of course his analysis will change accordingly. For instance, if we assume that we were able to survey all men that lived and identify "the longest-lived of men", let's say it was Adam, then we would be in a position to "know of him through history", and perhaps even attach biographical details based on the biblical account. Correspondingly, a person who knows little of history may well be in a position to infer nothing about "the first Chancellor of the German Empire" than what is forthcoming from the description itself.
In other words, while different people may use the same description, the scope of judgements that can be made based on this description depends on the knowledge of the person who is using the description, and is specific to that person. Moreover, it may expand as the person gains new knowledge, e.g. that the first Chancellor of the German Empire was one Otto von Bismarck, and gets acquainted with his biography. As Russell says, "knowledge concerning what is known by description is ultimately reducible to knowledge concerning what is known by acquaintance".
Russell differentiates in the whole chapter between knowledge by acquaintance and knowledge by description. Near the end of the chapter Russell emphasizes that knowledge by description must be reducible to knowledge by acquaintance,
Your question refers to his two examples of knowledge by description:
'the most long-lived of men' is a description of a unique person. Exactly one person fullfills that description. Nevertheless we do not know who this person is. The description is given by the two universals “man” and “most long-lived”. The listener of this description is unable to link it to any knowledge he has about a possible candidate.
'the first Chancellor of the German Empire' is a description too. Also this description refers to a unique person. But besides the abstract “Chancellor” the description contains the particular term “German”. This particular “German” facilitates that the listener links the description to a certain country. And via this link he further connects the description to the person of Bismark and to some historical knowledge by acquaintance which he has about Bismark.
Russell assumes that nobody is able to link the description ‘the most long-lived of men’ to a distinct person. You consider at the end of your post the different case that the listener is able to link the description to a distinct person, at all. On the basis of the listener’s knowledge by acquaintance. I agree with you, for such listeners the example would fall under the Bismark-case.