I'm curious to see what some other people think about this. — 83nt0n
I'm actually tempted to call it the 'problem of deduction'. — 83nt0n
It is not a problem for deductive logic so much as an observation about it: There is a difference between a premiss (such as A or B) and a logical leading principle (such as C and D and so on). The latter is also called an inference rule, and all other deductive inference rules can be derived from modus ponens once certain axioms are established. One must recognize that such rules are intrinsically truth-preserving in order to understand and employ deductive logic. The turtle is only compelled to accept Z if his goal is to adopt true beliefs.So I've come across a story (What the Tortoise Said to Achilles) that may pose some problems for deductive logic. — 83nt0n
Again, that is why it is a leading principle or inference rule for deductive arguments in general, not an additional premiss (or infinite series of premisses) in each individual argumentation that employs it.Deductive logic seems to require modus ponens to justify modus ponens. — 83nt0n
So I've come across a story (What the Tortoise Said to Achilles) that may pose some problems for deductive logic. I'm actually tempted to call it the 'problem of deduction'. I'm curious to see what some other people think about this. https://wmpeople.wm.edu/asset/index/cvance/Carroll — 83nt0n
How do you justify that definition?By justified I mean entailing that a person can believe the proposition and stay rational. — 83nt0n
How do you justify that assertion?The justification is what connects a belief to whether or not it's true. — 83nt0n
How do you justify that response?You might ask how something might be justified, I'd say I don't know. — 83nt0n
How do you justify that self-characterization?I am a skeptic. — 83nt0n
How do you justify that judgment?All methods of justification seem flawed to me, including deduction. — 83nt0n
How do you justify that definition? — aletheist
How do you justify that assertion? — aletheist
How do you justify that response? — aletheist
How do you justify that self-characterization? — aletheist
How do you justify that judgment? — aletheist
If that is your definition of justified, then modus ponens is entirely justified, since it always takes us from true beliefs to true beliefs. — Nagase
I think Tim layed it out nicely: no matter what game we play the rules must be established first before any player can proceed — ISeeIDoIAm
Ironically, you seem to apply modus ponens to this argument (If there is a requirement for linear propositional support, then we must embrace skepticism; there is such a requirement; therefore, we must embrace skepticism) — Nagase
How do you know that you do not know anything? How do you know that you want to have knowledge?My stance is that I do not know anything, but I (really) want to have knowledge, so I continue the search. — 83nt0n
We already have, but you claim not to accept it, even though you cannot avoid employing it.How do we establish a system of logic that allows us to know? — 83nt0n
How do you know that you do not know anything? How do you know that you want to have knowledge? — aletheist
We already have, but you claim not to accept it, even though you cannot avoid employing it. — aletheist
How do you know that you do not know this?I do not know this. — 83nt0n
How do you know that you could be wrong?I could be wrong. — 83nt0n
This is your third assertion in a row that something is true.However, skeptics like me do not assert as true what we're saying. — 83nt0n
Why should I believe you?We just explain how it appears to us to be able to hold a conversation. — 83nt0n
The inference rules of deductive logic, including modus ponens, are intrinsically truth-preserving; if the premisses are true, then the conclusion is necessarily true. What deduction cannot guarantee is that the premisses are true.Deductive logic (at least classical) seems unable to guarantee the conclusions it validates. — 83nt0n
Another assertion that something is true. Do you not realize that thoroughgoing skepticism is self-defeating? In order to be consistent you would have to be just as skeptical about skepticism as you claim to be about everything else.I do admit that I probably cannot avoid employing it, but this has no bearing on whether it allows us to know. — 83nt0n
What do you mean by "the original presupposition"?They are intrinsically true so long as the original presupposition rings true. — ISeeIDoIAm
This is your third assertion in a row that something is true. — aletheist
Why should I believe you? — aletheist
The inference rules of deductive logic, including modus ponens, are intrinsically truth-preserving; if the premisses are true, then the conclusion is true. What deduction cannot guarantee is that the premisses are true. — aletheist
They are intrinsically true so long as the original presupposition rings true. I think that's the point he's trying to lay out. — ISeeIDoIAm
Another assertion that something is true. Do you not realize that thoroughgoing skepticism is self-defeating? In order to be consistent you would have to be just as skeptical about skepticism as you claim to be about everything else. — aletheist
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