Hardly Here

Why spend hours wondering how to do something when you can ask ilan.

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Bob Geldorf writes in the Telegraph in regards the vote on changing the laws of “habeas corpus” in Britain

Still today, 800 years later, Magna Carta resonates: “To no man will we deny, To no man will we delay, Justice and Right.” Is that not grand, worthy of your vote? Is habeas corpus to be traduced in one sad moment of political expediency? Do we not clearly deny and delay Justice and Right when we imprison a person for 42 days without charge?

What existential threat do we face greater than those of the past 800 years? What great terror exists today that not civil war, not world war, nor recent other terrorisms could make our forefathers change the fundamental basis of this state? What is so dangerous that our oldest statutes could be upended for such a ha’p'orth of momentary panic?

I submitted an assignment a few weeks back in which I did not provide a complete answer to the last of seven question.

But often when I am stuck in a line or somewhere I think about the one part of the problem I failed to solve. And soon I will have a solution.. I hope.

Hannah (pronounced Chana) Neshamah Pillemer arrived 12th March 1919.

Baruch Ha-Ba!

Update: For those who are confused its 19:19 pm and the year is 2008.

AngloGold Ashanti Limited
Incorporated in the Republic of South Africa
Registration Number: 1944/017354/06)
ISIN Number: ZAE000043485
JSE Share Code: ANG
(”AngloGold Ashanti/Company”)
ELECTRICITY SUPPLY INTERRUPTIONS STOP ANGLOGOLD ASHANTI’S SOUTH AFRICAN MINING
OPERATIONS
Following notification from Eskom regarding interruptions to power supplies, AngloGold Ashanti has halted mining and gold recovery operations on all of its South African operations. Only underground emergency pumping work is being carried out. According to Eskom, the current situation arises from reduced generating capacity aggravated by problems associated with coal supplies to power stations caused by unusually heavy rainfall. Eskom has not yet indicated how long the present situation will continue but the company is in contact with the electricity supply body. The company will provide further information as it becomes available.

I am busy working on Assignment 1 for COS407 2008. (Mathematical Logic for Computer Science)

Q1 (iii) asks us to prove this proposition is valid using truth tables.

(A nand ( B nand C )) equiv (B nand ( A nand C )).

However this is not a valid proposition.
This can be seen clearly for the interpretation when A is true, B is
false and C is true.

(true nand ( false nand true)) euiv (false nand ( true nand true))
(true nand ( true )) equiv ( false nand (false)
false equiv true

Furthermore, Question 2 and Question 5 also asks us to prove that this same proposition is valid using a different method.
Obviously I can’t prove its valid. Unless I change the rules of logic. Hmmph.

And even more problematically Question 6 asks us to do something with the proposition (ie prove it is a theory of the Gentzen system G) that may not be possible. Its possible to prove something is a theory of the system, but its not so easy to prove a proposition is not a theory of the system (if even possible.)

(The only silver lining is that I understand enough to see that the question is faulty.)

I sent an email to the lecturer and she responded very quickly.

Here is her first response:

Hi,

Thanks for pointing this out. I’m not going to change the assignment now, so you should answer the questions with the given formula. E.g. give your counter-example for Question 2 (because this is a semantic argument), and draw an open tableau which builds a counter-model for Question 5.

Regards,

I then responded

Thanks, and for Question 6.

I have not actually read the section on Gentzen systems yet (that is this weekend’s task); I am assuming now that the proposition would not be a theory of the Gentzen system G?

So I assume I should prove that instead. (Forgive me if I am speaking nonsense as I have not yet studied this system.)

I appreciate your quick response!

As I was not sure if it was even possible to do what she suggested; but I have not yet studied the section to make sure if I am right. But I was right and I received this later response.

It’s not so easy to prove that a given formula is NOT a theorem in a Gentzen system. So instead of proving this, you can rather explain why this is not as simple a matter as with the tableau proof. I.e. why are Gentzen proofs not a suitable proof procedure to verify that a given formula is NOT a theorem.

Hope this helps!

So… I now know how to proceed and can stick with my time-schedule. (I want to get this assignment completed by the end of January).

I must admit I am very impressed with the quickness of the response from the lecturer.