Theme 1 - Theory of science

1. The question posed in the opening of the book is how do I know the world around me exists? To do this Russell introduces the notion of “sense data”, the sensory information we perceive by interacting with everything around us. Russell separates between sense-data and physical objects. For instance, we can doubt what exact color something has, or whether you see the thing the same way someone else sees the thing, or even whether there really are other people. What we can’t doubt know is that we have this sense-data, that no matter what is the actual cause, I am feeling the surface of an object and seeing it’s color. The realness of an object can be put into question, but never our perception of it.
   
   
2. Russell uses propositions as a sentence on the form ‘X is something’, that means stating this proposition reveals a property of X. Furthermore, a proposition is exclusive. That means, if i propose ‘X is the next prime minister’, what I mean is ‘X is the next prime minister, and no one else is’. However, we may not actually know the real X, for example if X was a historical person. We can still describe a proposition about an object named X as long as we know we describe a true statement of fact about the real X.
   
   
3. With definite description Russel means a description that identifies someone, or some object. The example he uses is ‘a man’, which is a description, contra ‘the man in the iron mask’, which is a definite description. When I say ‘a man’ i may refer to a number of objects, but ‘the man in the iron mask’ refers to one man in particular.
   
   
4. The chapters discuss truth, and in particular true knowledge. Russell holds that knowledge is not the same as ‘true belief’, as something we believe may well be true but if the belief was based on a false belief it cannot be said we have knowledge. This is all a bit complicated to wrap your head around, but if I, for example, make something up that you believe in, and the thing I made up actually come true, what you believe is also true. But you cannot be said to have knowledge, as your belief is only based on my random guessing. 
   
   
   Instead Russell builds a more complex system proposes two ways in which something can be known, by means of judgement or by means of perception. Judgement means, for example, if you know the hour of sunset, you may know when the sun is setting even though you’re not actually seeing the setting sun. Knowledge by perception on the other hand means knowing something by actually observing it. Russell points out that the first way, like all judgement, is liable to error. The second way on the other hand is only possible when the relation between different parts of a complex situation is perceivable. 
   
   
   In the end Russell concludes that what we firmly believe, if it’s true, can be called knowledge and what we firmly believe, if not true, can be called error. As not everything can be known with absolute certainty Russell also introduces a third term, probable opinion, and notes that the greater part of what would commonly pass as knowledge belongs there.
   
   
   In the next chapter Russell uses a theory by philosopher Hegel as an example of when great ambition has gone into attempting to prove that an apparent feature of the actual world is self-contradictory and therefore cannot be real. Russell argues that very little can come out of this. He uses the infinity of time and space as an example. While it appears apparent to Russell that time and space stretches out infinitely, and is infinitely divisible, this have not stopped philosophers from trying to disprove it. Russell ends the chapter by noting that in the case of infinite space and time, it was later proven infinity was not self-contradictory but rather contradictory of certain prejudice.