Summary of Philosophical theses from Russell:
Although it is common to consider analytic philosophy as having departed from a concern with the traditional problems of metaphysics and epistemology which characterized the "modern" period from Descartes through the British idealists, in fact Russell retains a fixed focus on the basic challenges of epistemology (to account for our "knowledge" of the world) and metaphysics (to give a general account of what it is to be "real").
In epistemology the following theses defended by Russell came to shape the character of much analytical philosophizing:In metaphysics Russell's conception of philosophy led to the following theses:
Knowledge is understood as something that can be expressed in a language (the "linguistic turn"). Knowledge expressed by a language is able to make true assertions about ("the facts") reality in virtue of its meaning. The unit of meaning in a language is a proposition. Propositions possess "truth value" (i.e. they are true or false) in virtue of what they assert about the "facts," i.e. what they mean. Propositions which correspond to the facts (see metaphysics below) are true; those which do not are false. Knowing whether propositions are true or false first requires knowing their meaning. Knowing the meaing of a proposition requires understanding what would make it true (the "fact" it asserts, its "truth conditions.") The meaning of ordinary language is too hopelessly vague for a precise expression of its truth conditions. An artificial or "ideal" language, the language of symbolic logic, is needed for precise expression of knowledge. Propositions in such an ideal language are complex symbols composed of simple symbols. The simple symbols in propositions which refer to things in reality are logically proper names. Particulars are the thing to which simple symbols refer. Understanding the meaning of a logially proper name requires being directly acquainted with that particular to which it refers. We are aquainted with these particulars in the form of sense data. In the experience of sense data the knower is directly aquainted with atomic facts. Knowledge consists primarily in complex propositions which are logical constructions from large numbers of simple atomc propositions. An atomic proposition is a complex symbol consisting of a name referring to a particular we are directly acquaitned with and a universal defining a set of particulars, thus our knowledge of the meaning of a proposition is knowdge by description. The philosopher's task, qua epistemologist, is the logical analysis of knowledge claims (i.e. propositions expressed in the ideal language of symbolic logic). The result of such an analysis is a clear statement of the meaning of each propsition, i.e. of what would make it true, to what fact would it correspond if true. The task of determining what the facts are belongs to the specific sciences concerned with the subject matter of that proposition. Propositions which are logically true, tautologies, state nothing about the facts; they are true no matter what the facts of reality are (true in all possible worlds); all such propsitions are analytic. Synthetic propositions (those which are not analytic) are true or false because of what the facts are; they cannot be known to be true by logical analysis (a priori, by reasoning alone); they can only be known a posteriori, i.e. by experience. Since knowledge is expressed in propositions, and true propositions are true because of the facts, the epistemological analysis of knowledge allows us to infer ontological conclusions about what reality must be like in order for us to have knowledge of it The epistemological analysis of knowledge requires the logical analysis of language and how it meaningfully refers to the world. Thus the logical analysis of language justifies inferences to ontological conclusions about reality. By Ockham's Razor there is no justification for postulating the reality of any kind of entity unless the logical analysis of language reveals that there must be such a kind of thing in order for language to truthfully refer to the "world." The world consists of the facts. The same facts, ("the world"), which make those true propositions true make false propositions false Complex facts can be known only because we can know the simple (atomic) facts of which they are "constructions." What are ordinarily called names are not logically proper names, because they are not simple, but refer to large sets or series of sets of sense data. Sets are defined by their extension (their members); to refer to a set requires the reality of nothing more than the particulars which are members of the set. Numbers are constuctions of sets of equinumerous sets; there is no need to postulate the independent reality of numbers. In each sense datum we are acquainted with (or "know by acquaitnance") a simple (atomic) fact in which that particular datum has a certain quality or stands in a certain relation to other paticular sense data.. In that sense datum we are directly acquainted with both what is particular and what is universal. Reality must include Universals and Particulars Sense data are neither material nor mental; "matter" and "mind" are both "fictions" constructed of "neutral" sense data. The physical objects of ordinary experience and language are "constructions" of enormous sets of sense data (neutral monism). Halucinations, "dreams," and other cases of non-veridical perceptions aree also real. Sense data are experienced in chronological succession as related to other sense data in being "before" or "after" in a series. Minds or persons are constructions of the same sense data arranged in different relations.