"A matter of logical form, as it were"

J quotes my:

"But logicians NEVER study the 'matter'. The point of validity is that it's 'formal validity'. Toulmin was criticised as offering 'informal logic' when what he offered (and failed) was 'material logic', rather."

and writes:

"Well....Aristotle hisself to the contrary. Categorical syllogism, Square of O.--all made use of, like, terms and defined objects (categories or arithmetic/geometry, perhaps). The premises--ie, matter-- were often an issue."

Yes, but he did use 'variables' -- letter schemata, which Lukasiewicz adored. Aristotle's true examples are so naive that it's best to ignore them:

"Socrates is white".

I cannot think _that_, under the full Athenian sun!

---

"albus Socrates est"

J adds:

"It's not just p -> q, but..."If human, then mortal." While the formality is important, it's not the end of the matter--"

I like that. We should start using 'matter' more formally in our conversations.

"else we should agree to Wittgenstein's view of logic as merely a play of tautologies, and go back to chess."

Witters was pretty confused, and the fact that he wrote the Tractatus in the trenches did not help. What he said about Russell's merit having discovered that an apparent logical form is not a real logical form is so tautologous that I want to scorn Hacker about it.

J adds:

"Besides, as the fiendish Goedel showed, it's not a perfect system. The best you get is First Order completeness, IIRC: if an argument is valid, the system shows it as such. But it doesn't always show invalidity (ie, the halting problem). Second order is incomplete."

Yes. That's an excellent point. What is the USE of all those quantificational logic sybolisms, since, after all, quantificational logic does not rest on a sound conception of valdity. I might just as well pick cherries in the fields!

So perhaps 'validity' has been overestimated.

J adds:

"Im not sure I would call Toulmin's schema informal logic. It's a type of...induction--ie, his argument structure was aimed at evidentiary issues--social sciences, medicine, law, history--not merely deductive."

Yes. Good point. We should recall that Mill's System of Logic (as a proper Victorian thing -- although I think he wrote it before Victoria was a queen) had two volumes: Deductive and Inductive. What a genius! It is sad that for all we love Lewis Carroll he was perhaps responsible for the demise of inductive logic, but then perhaps he wasn't. It was such a priority for all those British logicians of Mill's day. Material logic, they would call it perhaps.

Strawson's flirts with "Inductive logic" in Intro. to logical theory are so superficial that it's no wonder Grice wanted to pay due respects to probability in "Aspects of Reason".

J notes:

"I mean, there are many formal logic apps. you can download and test whether a valid conclusion follows from a set of premises--like a Quine bot, about likes a chess bot. But there aren't apps which can easily prove say, what caused the Great Depression. Or the mortgage crisis. Or WWII. Or the roots of poverty, etc."

Yes. We have one logic too many.

"The logic of preference"
deontic logic
alethic logic
practical logic
formal logic
informal logic
pragmatic logic
semantic logic
logic of probabilities
relevant logic
prothetic logic

and so on.

It seems almost anyone (every one?) is building his own logical system (Grice, System G).

No wonder Mc wrote: "Everything you always wanted to ask about logic* but were afraid to ask".

----

It would or may do to revise collocations applying and modifying 'logic'. It seems there is quantum logic, and a logic for each department of science. I'm less sure about the logic historians or sociologists use, so J's examples above are very much on spot, as they say.