Actually the method of tables rely on the interpretation of the logical connective, in regards to enunciative logic.
Modus ponens is indeed a completely different thing: it is a valid argumentative form. Thus, it presupposes an enunciative theory to be connected to.
No. "Proof" is defined by the axioms and inference rules one adopts. Ergo, there's no way to independently prove the validity of such things because proof and validities are what you get from the above things. — MindForged
There are two errors: 1 proof is not 'defined' either by axioms or inference rules. Proof is the results of applying inference rules by means of axioms. This is not at all a definition, just as the egg is not a definition of the chicken.
2 It is false that you can not prove validity of 'such things'(axioms? rules of inference?) independently(even if your statement is incomplete, because you do not specify independent from what). The proof of a logical theory is obtained by verifying the coherence of axioms, i.e. through the non contradiction principle in a certain form: iff from the set of axioms you can not derive, through rule of inference, a contradiction, then the set of axiom is coherent. You can even proof the independency of some axioms from others by verifying that the same theorem deducible by n axioms+ x axioms is deducible even just through n(or x) axioms.
Of course do not exist an absolutely independent way to proof something, because a demonstration itself is defined as the derivation of something from something which is different, and this IN ACCORD TO A RULE(or how else is to be recognized as a relation of derivation and not a succession?). There is always a reference to establish the recognition of a result from the relative process. And this you say:
So the notion of a purely independent proof, of "laws of thought" or absolute, inescapable presuppositions that need no proof is just an incoherent idea. — MindForged
But not because it is incoherent, but because is IMPOSSIBLE.
I am not saying that rules of inferences are eo ipso processes: yet to us at least there is a correspondent process, through which we infer from something to something different.
The rules do not claim for proof because they are a process. Just as you do not search the proof of the friction causing your car to adhere to the ground, but an explanation of it, which is a completely different thing, and not at all a logical proof.
Being logic the form of thought in general, it is a necessary condition to be SATISFIED in order to have some way at all to distinguish a process and its results. Once satisfied, we have the condition under which proofing has a form at all, recognizable.
Inference are by definition NOT deductions. Ergo they are NOT proofs. They are simply refined conjectures. And that is what Science is all about. That is why Science is NOT Philosophy. — hks
Here is a classic confusion( which MindForged did not make) between a method to obtain a proof and a proof, i.e. between say something THROUGH a language and to say something ABOUT a language.
Inference are what renders possible to distinguish at all a logical difference, and since this is the basis of thought in general, without it would be missing the GROUND to proof something. This is the reason why inferences can not be proved, because by RULES OF INFERENCE a ground to proof is furnished, and THEN inferences are made to obtain proofs, after the logical form has been interpreted, and thus there is an object at all as the material to realize the structure of inferences, and Then to infer.
Inferences are not at all relying on definitions, because they are of a different status(logically): a definition is an EQUIVALENCE(hence it presupposes a logical structure too, and is a PROPOSITION) while INFERENCE is the PROCESS through which from NOT EQUIVALENT propositions, one is obtained from others. And a process is not defined, but IDENTIFIED, such as gravity is not defined ny the gravitational law, but its EFFECTS are recognizable insofar as they are measurable through that law, which is so far to be a definition of gravity that it is gravity that made possible to discover the laws. The laws of course are conformant to a structure of general thought, which is the only postulate we need.
Your deeply confused view is evident in the next sentence
They are simply refined conjectures — hks
in which you clearly confuse an operation on propositions(inference) with a proposition( conjectures are propositions).
Science is so far from being a pretty little thing of conjectures, that conjectures are propositions not rigorously proved, while proofs are propositions rigorously proved and those, in a systematic unity, constitutes what every rational being call 'science'. A bunch of conjectures, without a system in which they may be proved are just grammatical fantasies.
That is why Science is NOT Philosophy. — hks
Being clear that you got wrong giving your account on what science is(or should be in accord to your thoughts of course) I would be curious to hear the difference between science and philosophy, being each science a coherent and consistent system of conclusions obtained through rule of inferences from objective premises. If philosophy is not science is just a fable, as everything with no math and no logic
.
'm not being verbose. You said inferences are by definition not deduction. I'm just asking you what definition are you using, because I pointed an exemple of a deductive argument made by an inference.
But then I realized that an inductive argument contains inferences as well, so an inference cannot be a deduction. You could just answer my question instead of being defensive. — Nicholas Ferreira
This is a very educate behavior and to me an index of a truly inquisitive, instead of rhetoric, nature.
You are totally correct Nicholas: you recognized that our Great Master Hks would like to teach us(or to put blame on our supposed inferiority in regard to his great mind) Logic, but he don't even know the difference between an operation(inference) and the validity of an argument, for both induction and deduction are inferences, and both can be valid, hence they differ logically(i.e. in respect to validity) just in respect to the truth of the premises. He confuses deductive/inductive(which is psychological) and deductively/inductively VALID(which is logical).
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The claim that
the truth table is the conjunction of the premises implying in the conclusion
— Nicholas Ferreira
does not seem correct. There is nothing inherent in the definition or concept of a truth table that identifies it as being anything other than a tabular representation of the possible binary values assigned to some variable. Consider the simplest truth table:
A | A
_____
T | T
F | F
Which just says the variable "A" has the values assigned to it. There is nothing here about "conjunction" or "implication". Truth tables can further be used to define what certain operators like conjunction and implication mean by showing how the values assigned to variables change when the operator is applied to them. At this point truth tables are used to introduce the notions of conjunction or implication or whatever, but they don't purport to prove anything about these operators. Once you have defined what the operators are, you can construct tautologies that are the functional equivalent of the rules of inference that show that the rules preserve the truth values of the variables they're applied to because they are, well, obviously true as tautologies. The rules of inference then are just short hand ways of constructing these tautologies that are more convenient to work with. — Mentalusion
Here is a person who reflects before writing. Not surprisingly he said something clear, in a very educate manner, and also correct; also with some interesting elements of originality: «truth tables are used to introduce the NOTIONS of...» in a somewhat 'diagrammatic' view of recognition(not merely linked to processes).