Ideas from 'Human Knowledge: its scope and limits' by Bertrand Russell [1948], by Theme Structure

[found in 'Human Knowledge' by Russell,Bertrand [Routledge 2009,978-0-415-47444-3]].

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5. Theory of Logic / E. Structures of Logic / 2. Logical Connectives / c. not
Is it possible to state every possible truth about the whole course of nature without using 'not'?
                        Full Idea: Imagine a person who knew everything that can be stated without using the word 'not' or some equivalent; would such a person know the whole course of nature, or would he not?
                        From: Bertrand Russell (Human Knowledge: its scope and limits [1948], 9)
                        A reaction: Nowadays we might express Russell's thought as 'Does God need the word 'not'?'. Russell's thesis is that such words concern psychology, and not physics. God would need 'not' to describe how human minds work.
10. Modality / A. Necessity / 6. Logical Necessity
Some facts about experience feel like logical necessities
                        Full Idea: The impossibility of seeing two colours simultaneously in a given direction feels like a logical impossibility.
                        From: Bertrand Russell (Human Knowledge: its scope and limits [1948], 9)
                        A reaction: I presume all necessities feel equally necessary. If we distinguish necessities by what gives rise to them (a view I favour) then how strong they 'feel' will be irrelevant. We can see why Russell is puzzled by the phenomenon, though.
12. Knowledge Sources / D. Empiricism / 5. Empiricism Critique
It is hard to explain how a sentence like 'it is not raining' can be found true be observation
                        Full Idea: If 'it is not raining' means 'the sentence "it is raining" is false', that makes it almost impossible to understand how a sentence containing the word 'not' can be found true by observation.
                        From: Bertrand Russell (Human Knowledge: its scope and limits [1948], 9)
                        A reaction: Russell goes on to explore the general difficulty of deciding negative truths by observation. The same problem arises for truthmaker theory. Obviously I can observe that it isn't raining, but it seems parasitic on observing when it is raining.
19. Language / F. Communication / 3. Denial
If we define 'this is not blue' as disbelief in 'this is blue', we eliminate 'not' as an ingredient of facts
                        Full Idea: We can reintroduce 'not' by a definition: the words 'this is not blue' are defined as expressing disbelief in what is expressed by the words 'this is blue'. In this way the need of 'not' as an indefinable constituent of facts is avoided.
                        From: Bertrand Russell (Human Knowledge: its scope and limits [1948], 9)
                        A reaction: This is part of Russell's programme of giving a psychological account of logical connectives. See other ideas from his 1940 and 1948 works. He observes that disbelief is a state just as positive as belief. I love it.
27. Natural Reality / A. Classical Physics / 1. Mechanics / a. Explaining movement
Russell's 'at-at' theory says motion is to be at the intervening points at the intervening instants
                        Full Idea: To reply to Zeno's Arrow Paradox, Russell developed his 'at-at' theory of motion, which says that to move from A to B is to be at the intervening points at the intervening instants.
                        From: report of Bertrand Russell (Human Knowledge: its scope and limits [1948]) by Stathis Psillos - Causation and Explanation 4.2
                        A reaction: I wonder whether Russell's target was actually Zeno, or was it a simplified ontology of points and instants? The ontology will also need identity, to ensure it is the same thing which arrives at each point.