- #71
JesseM
Science Advisor
- 8,520
- 16
But you still haven't given a coherent explanation as to what you think the flaw in the demonstration was. All your talk about the conclusion being included in the premises was obviously irrelevant to showing that the demonstration is flawed, since you've agreed there are plenty of if-then conditionals where the conclusion is included in the premises and yet you believe the if-then statement is true.Austin0 said:This IS the question. Based solely on these stated premises, I think that it is not inherently inevitable or adequately demonstrated that this is neccessarily true.
Perhaps it would help if you answered another question. Do you agree that the premise [the laws of physics respect relativity AND FTL signalling is physically possible] is synonymous with the premise [the laws of physics respect relativity AND there is some inertial frame where, if we consider the difference in space coordinates dx and the difference in time coordinates dt of the events of a signal being sent and received, then dx > dt (in units where c=1)]? Do you agree that in any hypothetical universe where the first statement applies, the second statement should apply too, or do you think it is meaningful to talk about a hypothetical universe where the first applies but the second does not?
You can only include the initial and final conditions as premises if you have already checked they are consistent with "the pertinent applicable molecular physics". If it is impossible that the specified final outcome could follow from the specified initial conditions according to the specified laws of physics, then you're using logically inconsistent starting assumptions. Of course, you're free to drop any specific assumptions about the laws of molecular physics beyond the notion that the laws of physics are such that the initial conditions would lead to the specified final outcome--no matter what initial and final conditions we choose, presumably some possible laws would predict that the initial condition would lead to the final one.Austin0 said:If, for example , the question was the hypothetical empirical question of a chain of catalytic reactions. With several possible, reasonable quantitative outcomes.The question and conclusion being the quantitative outcome of the intermediate one.
The Axioms: the pertinent applicable molecular physics.
Premise #1: the initial quantitative combination.
Premise #2: the final quantitative outcome.
Isn't it true that in any proof where the conclusion follows mathematically or logically from the starting assumptions, the conclusion is included in the premise? That still doesn't show why the demonstration is false. If it's mathematically impossible that there could be a universe where the laws were such that the premises were true (including both the initial and final results and whatever constraints you want to place on the laws of physics) but that the "specific intermediate result" did not occur, then surely that means the if-then conditional "IF [specified initial condition + specified final condition + specified laws of physics, if any] THEN [specified intermediate result]" would be true! Do you agree? If so, this has no relevance to showing why the if-then conditional about FTL and backwards-in-time signalling is false.Austin0 said:Which itself was only possible through a single specific intermediate result and also directly determined the intermediate result.
What would you say in this case ? If this was presented as a demonstration or proof of the intermediate quantitative result, would you possibly agree that this could be described as including the conclusion in a premise?
What part of it would be subject to empirical determination? If you found that the final conditions didn't follow the initial conditions, that would show your premises were false, but it wouldn't show the if-then conditional "IF [specified initial condition + specified final condition + specified laws of physics, if any] THEN [specified intermediate result]" was false. An if-then conditional is only false if it's logically possible for the premises to be true while the conclusion is false, as long as that's not logically possible then the if-then conditional is true, regardless of whether the premises are true or not in the real world. On the other hand, if all the premises were found to hold but the conclusion did not, then you must have been wrong when you said that the premises were "only possible through a single specific intermediate result and also directly determined the intermediate result".Austin0 said:Of course in this situation it would be subject to direct empirical determination while tachyons are so hard to catch.
No problem, see my post above.Austin0 said:It would be great ,if you have time, to get your perspective on my post #65