display all the ideas for this combination of texts
3 ideas
12611 | Necessity makes alternatives impossible [Aristotle] |
Full Idea: Necessity is what makes it impossible for something to be other than it is. | |
From: Aristotle (Metaphysics [c.324 BCE], 1015b03) | |
A reaction: Note that necessity here seems like an active force, rather than a mere description of a logical or metaphysical state of affairs. The underlying idea seems to be that essences enforce necessities, but it doesn't say that here. |
16490 | Some facts about experience feel like logical necessities [Russell] |
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. |
17852 | A thing has a feature necessarily if its denial brings a contradiction [Aristotle] |
Full Idea: If anything has the property of being perishable it has it of necessity, on pain of one and the same thing being perishable and imperishable. | |
From: Aristotle (Metaphysics [c.324 BCE], 1059a05) | |
A reaction: Of course the perishable could become imperishable over time, without contradiction. This illustrates the foundational idea that a proposition is necessary if its negation is a contradiction. [...actually this argument is invalid as it stands!] |