A first look at the Russell’s principle
§1. The Russell’s principle plays a major role in Evans (1982). The whole book, in fact, can be seen as an attempt to clarify and apply this principle to various cases (for example, to delineate the boundaries of demonstrative identification). The basic intuition is simple (89): in order to make a judgment about an object, a certain kind of knowledge of that object is required. Obviously, the difficult part is to give a proper theoretical characterization to this intuition. Which kind of knowledge is intended here? Before answering this question, however, it has to be noticed that this is not the only way to formulate the principle. In particular, through the whole book (and in more recent discussions) the principle is sometimes intended not as specifying which kind of knowledge is required to make a judgment about an object, but rather which knowledge is required for thinking about an object. This last idea can be formulated as follows: in order to have a thought about an object, a certain kind of knowledge of that object is required.
§2. How did Russell specify the principle? Evans refers to p. 58 of The Problems of Philosophy: “The fundamental principle in the analysis of propositions containing descriptions is this: Every proposition which
we can understand must be composed wholly of constituents with which we are acquainted.” (Russell, 1912: 58) Thus the crucial concept employed by Russell is that of understanding. [Two papers that I found useful are: Baldwin (2003) From Knowledge by Acquaintance to Knowledge by Causation. In The Cambridge Companion to Bertrand Russell, and Sainsbury (1986) Russell on acquaintance.]
§3. Even though for Evans the notions of understanding, thinking and judging are related, nonetheless they are not equivalent. It seems that we can schematise their connections as follows: no object -> no thought -> no understanding -> no judgment (and, we can add, no meaning).
§4. The idea behind the Russell’s Principle is that to have a thought about an object, in a proper sense and in a way that does not just imply being able to say something (which can be not related to that object), we need to have the capacity to discriminate that object, that is, the capacity to have a conception of a world of such objects. In other terms, we need a certain kind of discriminative knowledge of that object. The specific discriminative knowledge required is not the same for all objects: to have thoughts that can be expressed with sentences containing ‘that man’, we need a particular capacity (or Idea) that is appropriate for this kind of identification.
§5. Case 1. Nicola is completely oblivious of who Marco F. is. He has never met him and never heard of him. If one day Nicola walks around the street of his city and sees a graffiti on a wall saying: ‘I love Marco F.’ (and the author of this graffiti intended to refer to Marco F.), has Nicola obtained the capacity to entertain thoughts about Marco? If I have understood well what Evans is aiming at, the answer should be no. Why? Because Nicola does not have any capacity to judge as true a particular-proposition involving Marco having the general form「δ is m」where ‘δ’ is an Idea of an object. In other terms, he does not have the capacity to discriminate Marco. In Evans’ terminology, Nicola does not have the Idea of Marco. What is the Idea of a particular object? “An Idea of a particular object is part of a conception of a world of such objects, distinguished from one another in certain fundamental ways. For every kind of object, there is a general answer to the question ‘What makes it the case that there are two objects of this kind rather than one?’” (106). Each object is associated with a fundamental ground of difference, that is, an answer to the question ‘what differentiates this object from others?’ It is not completely clear to me whether this is enough to vindicate the intuition that in order to have a thought about a particular object we need a particular kind of connection with that object. In the above example, probably Nicola has what it takes to distinguish one person from another and thus, if it is excluded that the expression ‘I love Marco F.’ was referred to an animal, then, after all, he had the kind of knowledge required. However, it is still true that if Nicola met Marco on the street, he would not have the capacity of discriminating him from other people. I am not sure whether this idea is correct, but it seems that the discriminatory knowledge that is required by the original intuition behind the Russell’s principle cannot be accommodated solely by talking about a fundamental ground of difference, where this notion is understood, more or less, as a sortal concept. Comments are welcome.
§6. “Particular propositions are propositions the specification of whose content involves the use of a singular term” (109) A particular thought involves an Idea of an object (a capacity of thinking of the object) , the entertaining of a proposition to the effect that the object of the Idea is such and such. It has to be remembered that, strictly speaking, according to Evans, an Idea does not occur in a proposition.