A logical proof
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SpeedOfSound wrote:I am still uncomfortable with mixing ontological categories.


Panderos wrote:If nothing exists, then the fact "if pineapples existed, they would be yummy" also exists. I mean you don't need to resort to the 'nothing exists' fact.


Panderos wrote:So "nothing exists" means "facts don't exist" but we can still have conditional statements in the world of nothing? Billions of conditional statements, trillions, the world of nothing is packed to the brim!

Teuton wrote:
I haven't done so. When I say that objects exist and facts exist, the difference between these two categories is not due to there being two different meanings of "exist". The proposition <nothing exists> excludes all categories of entities whatsoever from existence. That is, if nothing existed, there wouldn't be any objects/substances, properties, relations, facts/states of affairs, states, processes, or events.

DrWho wrote:
Doesn't this primarily concern how we think? I can't think that 'nothing exists' since it is logically impossible for 'nothing' to 'exist'


andrewk wrote:Very nice. Sadly though, if we accept the postulate (1) then no laws of logical inference exist, including Modus Ponens (used for 4 and 5) and the law of excluded middle (used for 6, which I think is the key step). So the reductio ad absurdum cannot be performed, and the conclusion cannot be reached.

Teuton wrote:Panderos wrote:So "nothing exists" means "facts don't exist" but we can still have conditional statements in the world of nothing? Billions of conditional statements, trillions, the world of nothing is packed to the brim!
No, if there were nothing, there wouldn't be any statements or propositions either.


Panderos wrote:
But you're saying that if nothing exists, the fact 'nothing exists', exists. Therefore we have a paradox and we can't have the nothing state.
Panderos wrote:
Why can't I say that if nothing exists, some random conditional statement exists (which is also true in the nothing world, like your fact), which also gives us a paradox yada yada..?

It's actually all based on alphabeti spaghetti. At lunch, Frege came across A A ⊃ B. He ate the As and the U, and was left with just the B. From this insight, most of logic was born.andrewk wrote:This question makes me start to wonder whether the whole component of metaphysics devoted to the concept of "possible worlds" lacks validity. Reasoning about what worlds are possible is done using rules of logical inference that we have adopted based on our observations of this world. For example, we repeatedly observe that if A->B is true and A is true then B is true, and after we have observed this enough times for different As and Bs we use the Principle of Induction to infer the Modus Ponens logical rule that ((A->B) & A)->B.

When it comes to formal logic, understanding and technical competence go hand in hand, just like with algebra. If someone tries to solve the quadratic equation x^2 = 0 by laboriously carrying out every step in the "completing the square method", I'll tell them they don't (yet) understand elementary algebra. Similarly, when you write the sort of formalisation in your OP, and then fail to register its immediate simplification, I'll tell you that you don't understand elementary formal logic.Teuton wrote:You don't know what I understand and what I don't understand, so shut up!

Teuton wrote:1. It is not the case that something exists. [assumption #1]
2. If it is not the case that something exists, then the negative fact that it is not the case that something exists doesn't exist. [assumption #2]
3. If the negative fact that it is not the case that something exists doesn't exist, then it is not the case that it is not the case that something exists. [assumption #3, instance of: the fact that p exists <–> it is the case that p]
4. The negative fact that it is not the case that something exists doesn't exist. [from 1+2 by modus ponens]
5. It is not the case that it is not the case that something exists. [from 3+4 by modus ponens]
6. Something exists. [from 5, instance of: ~~p <–> p]
7. Something exists and it is not the case that something exists. [from 1+6 by &-introduction]
8. Therefore, necessarily, something exists. [from 1+7 by reductio ad absurdum]
Q.E.D.

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