Theme 1: Theory of science

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

What is real and what is not, true or false? If it is true, how can we now for sure? Russell introduces the notion ”sense-data” as something when we perceive an object through our senses like colors, sounds, smell, flavor and feel. If you pick up an object such as an apple, you can see the color and the shape of the apple and how it feels when you touch it. Different people can for example interpret the colors differently, is it still the same object? Without someone seeing or touching the apple, does it still exist?

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?

Proposition is what we know by knowledge of description. Certain and specific knowledge we are not acquainted with and thus we don’t know if it’s really true or not.

Statement of fact is a collection of our experiences and things we are acquainted with which has led to a belief. In science scholars often introduce propose new findings and theories and when the propositions are backed up with facts they become statements of fact which we generally consider being true.

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

In this chapter Russell makes a distinction between two kinds of knowledge. Knowledge by acquaintance is a kind of knowledge you get from the sense-data which makes up the appearance of an object.  Knowledge by description is gained from having something explained to you, not from experiencing the object.

Russell further divides knowledge by description into two different kind of knowledge, ambiguous and definite description. The difference between the two is how specific the knowledge is about the object or person. An example of an ambiguous description could be “a man”. You don’t know anything really about this person except it’s a man. Definite description is more certain, i.e. “the man with the iron mask”, which is more specific to just one man.

In chapter 13 ("Knowledge, Error and Probable Opinion") and in chapter 14 ("The Limits of Philosophical Knowledge") Russell attacks traditional problems in theory of knowledge (epistemology). What are the main points in Russell's presentation?

One could think that knowledge and true belief would be the same thing, but Russell makes the case that it’s not. True belief can’t be knowledge when it’s deduced from false belief. For example, if I get a correct answer on a math test one might consider that knowledge, but if I reached the answer by incorrect reasoning it can’t be considered knowledge.

Russell talks about a man who believes the late Prime Minister’s last began with a B. The belief was true since the Prime Minister’s last name was Bannerman. But if the same man had thought the last name was Balfour, he will still believe the late Prime Minister’s last name began with a B. His belief would still be true, but wouldn’t be thought to constitute knowledge. So true belief shouldn’t be considered knowledge since it can be derived from fallacious processes.