Theme 1: pre-reflection

What does Russell mean by "sense data" and why does he introduce this notion?

Russel's defines as sense-data the things immediately known in sensation. Not the sensations themselves, but the objects of the sensation – what is sensed. He exemplifies by saying that you can have a sensation of a colour (e.g. green), but the colour itself, he says, is not a sensation, but a piece of sense-data.

The concept of sense-data is vital to his discussion about the ontology of matter (physical objects) and how we experience it. He proposes that we cannot directly know anything about a physical object apart from the set of sense-data we associate with it. What sense-data about an object we are able to experience through sensation varies, of course, depending on our physiology and our relation to the object. Colours of objects, for instance, depends on how light is reflected by them and how we catch those reflections in our pupils. Thus, both spatial relation as well as the physiology of our sensory organs affect what sense-data we get a sensation of.

What is the meaning of the terms "proposition" and "statement of fact"? How does propositions and statement of facts differ from other kinds of verbal expressions?

When Russel speaks about propositions he speaks about the logical meaning of a statement. He is pointing to the meaning behind the language: the propositions are the carriers of meaning. The same proposition could be stated in different ways, depending on how you order the words or what language you use, for instance.

Propositions and statements of fact differ from other forms of linguistic expressions in that they predicate something about reality, they have a truth-value that can be evaluated. The building blocks of propositions are, according to Russel, objects and properties. The meaning of a proposition then, depends on what objects and properties it contains, as well as it's structure (what is predicated about what).

Russels propositions are closely related to logical form; if two verbal statements are said to represent the same proposition, they have to have the same logical form.

In chapter 5 ("Knowledge by Acquaintance and Knowledge by Description") Russell introduces the notion "definite description". What does this notion mean?

A definite description is a description that refers to a definite entity. (an entity that can could be named.) In classical meaning-theory, Russels definite descriptions would be descriptions of names or singular terms (terms that have a reference), as opposed to general terms (which have an extension; a set of referenced objects if you will).

He uses the term definite description to differentiate between such descriptions and ambiguous descriptions, that is, a description that points out something general (the so-and-so versus a so-and-so).

In chapter 13 and in chapter 14, Russell attacks traditional problems in theory of knowledge (epistemology). What are the main points in Russell's presentation?

Russel puts forth a view on truth that is very well aligned with the idea of the scientific method. He discusses truth, falsehood and probable opinion, and concludes that most of what we know should be considered probable opinion.

He is confident that truth cannot just be true belief, but argues that it must have some sort of justification. This line of arguing isn't new, but can be traced back to Plato. The sort of justification he proposes brings him to a circular definition: True belief based on known premisses. This he solves by proposing two different definitions.

Truth, he says, can be derivative or intuitive, and derivative truths should be able to be reduced to intuitive truths, making the latter the more interesting of the two in analysis.

He further structures his understanding of intuitive knowkedge by claiming that we can have knowledge about truths (judgments), and knowledge about things (acquaintance). The latter category here, he determines, is the only one that can produce infallible truths, becasuse we cannot be acquainted with something that does not exist. This leads him to the issue of how these truths seem to be self-evident. 

He discusses these self-evident truths, which I understand as a priori truths that don't neccessarily have to be absolute, but has an element of relativity. The absolute self-evident truths are those most closely connected with our immediate sensory experiences, memory and perhaps self-conciousness.

The most interesting part of his chapter on the limits of knowledge, I think, is his reflections on how new scientific discoveries seem to thwart metaphysical speculation of the kind that was prominent during the 17th trough 19th centuries. He comes off as very scientifically optimistic and emphasizes how a lot of old contradictions have been proven illusory by modern science. He, being a logician, proclaims that logic has gone from barring possibilities to liberating the imagination, giving us tools for imagining all possible worlds. Philosophys role in this should be as the watchdog of the other sciences, if I interpret him correctly. An objectively critical science, not primarily aimed at supplying answers, but upholding intellectual earnesty.