Pains occupy a distinct and vital place in the philosophy of mind for several reasons. One is that pains seem to collapse the appearance/reality distinction. If an object appears to you to be red it might not be so in reality, but if you seem to yourself to be in pain you must be so: there can be no case here of seeming at all. At the same time, one cannot feel another person’s pain, but only infer it from their behavior and their reports of it.

— Wikipedia on Private language argument

2013.03.31 Sunday ACHK

惜此際 2.1

這段改編自 2010 年 4 月 3 日的對話。





— Me@2013.03.29

2013.03.30 Saturday (c) All rights reserved by ACHK

The Metagame

I’ve been bored at work for many reasons at many different times, but three things stand out as real killers:

1. working on the same project with the same people for years and years,

These are the symptoms of a problem, not the cause, and I think most jobs will have elements of them. But surprisingly it turns out that – for programmers at least – boredom is a choice. Recently, I chose not to be bored. I chose to think one abstraction level higher. I chose to play the metagame.

— Work Is Fascinating: The Metagame

— Mark O’Connor

2013.03.28 Thursday ACHK


這段改編自 2010 年 6 月 15 日的對話。

記住,你們現在的物理,正在奪 A 當中。因為高考課程的物理,所需的天份很少,只要你貫徹執行正確的讀書策略,自然會得到上佳成績。


— Me@2013.03.27

2013.03.27 Wednesday (c) All rights reserved by ACHK


Live forever! 2

In the long term, we’re still focused on becoming the place for people to post forever — a stable platform that will operate without worries of the site, team, or mission disappearing. We’re exploring options around becoming a non-profit entity to support the goal of data preservation, which is very different from other sites which are as a rule for-profit entities. With the death of Google Reader, we think that it’s increasingly clear that certain types of social software need to be outside the auspices of entities pursuing pure profit motive at the expense of its users.

— Garry Tan

2013.03.26 Tuesday ACHK

朋友 2

這段改編自 2010 年 4 月 3 日的對話。





— Me@2013.03.25



2013.03.25 Monday (c) All rights reserved by ACHK

Uncertainty principle, 6.3

The observer is not disturbing the individual particles, influencing the individual measurement results.

Instead, by joining the system, the observer is replacing the original system by a bigger one. The observer is not just disturbing, but actually changing the whole system, influencing the statistics of the measurement results of that system.

— Me@2013-03-22 01:32:47 PM

2013.03.25 Monday (c) All rights reserved by ACHK

Hacker 3


The Jargon File has had a special role in acculturating hackers since its origins in the early 1970s. Many textbooks and some literary works shaped the academic hacker subculture; among the most influential are:

* Hackers: Heroes of the Computer Revolution, by Steven Levy
* Godel, Escher, Bach, by Douglas Hofstadter
* The Art of Computer Programming (TAOCP), by Donald Knuth
* The Mythical Man-Month, by Brooks
* Compilers: Principles, Techniques, and Tools (“the Dragon Book”), by Aho, Sethi, and Ullman
* Structure and Interpretation of Computer Programs (SICP), by Abelson and Sussman
* The C Programming Language (K&R), by Kernighan and Ritchie
* The Hitchhiker’s Guide to the Galaxy, by Douglas Adams
* The Tao of Programming, by Geoffrey James
* The Illuminatus! Trilogy, by Robert Shea and Robert Anton Wilson
* Principia Discordia, by Greg Hill and Kerry Thornley
* The Soul of a New Machine, by Tracy Kidder
* The Cuckoo’s Egg, by Cliff Stoll
* The Unix System, by Stephen R. Bourne
* Hackers & Painters, by Paul Graham
* The Cathedral and the Bazaar, by Eric S. Raymond
* The essays of Richard M. Stallman (many published in Free Software, Free Society: Select Essays of Richard M. Stallman)

– Wikipedia on Hacker (programmer subculture)



[10] “Hacker” here means a highly skilled programmer, not a computer criminal. — Me

The basic difference is this: hackers build things, crackers break them. — Eric S. Raymond

In academia, a “hacker” is a person who follows a spirit of playful cleverness and enjoys programming.

– Wikipedia on Hacker (academia)




2010.03.04 Thursday ACHK

試前暑假 1.2

最近五年 3

這段改編自 2010 年 6 月 15 日的對話。



那時開始,你就可以狂轟 past paper(歷屆試題)。當年我高考的 Pure Maths(純數學),就是在公開試之前的那個暑假,開始做 past paper。我最終做了大約二十年的 past paper。

我考的那一屆是 1999 年。我由大概 1979 年的那一份 past paper,做到 1993 年的那一份。至於最近的五年的試題,1994 年至 1998 年,則留待 study leave(試前休假)才做,以作 mock 卷(模擬試題)之用。

做那二十年的 past paper,工作量實在驚人。一年的 past paper,有卷一和卷二,各自也要花三小時。即是一年兩份的 past paper,最低消費是六個小時。那還未計算,批改和改正的時間。

當然,你未必需要好像我那麼神經緊張,做足二十年的 past paper。但是,如果你打算做超過十年的試題,而又不在暑假時開始做,你大概不會有足夠時間,在你真正的公開試前完成。

當年,我由 1979 年的試題開始做,每個星期做一年兩份。到大概聖誕假時,我就完成了 1979 至 1993 年的題目。那時,還未到 study leave,所以,我還未可以開始做 1994 年至 1998 年的題目。於是,我重新由 1979 年的試題開始,再做一次。

— Me@2013.03.24

2013.03.24 Sunday (c) All rights reserved by ACHK

Uncertainty principle, 6.2

In another sense, the quantum uncertainty that the uncertainty principle refers to is due to the observer effect.

To measure a physical quantity of system, you have to add a measurement device into the original system, forming a bigger system. In other words, the disturbance is so huge that you do not call it “disturbance” anymore. Instead, you are actually changing the system.

Since the system has been replaced by a new one, the statistical patterns of the potential measurement results change.

— Me@2013-03-11 3:40 PM

2013.03.22 Friday (c) All rights reserved by ACHK

試前暑假 1.1

這段改編自 2010 年 6 月 15 日的對話。

所以,記住要有系統地,「按年份、計時間、計分數」做 past paper(歷屆試題)。

然後,在下一個星期,你就要「按課題」做 past paper。第三個星期,則要再「按年份」,如此類推。換句話說,「年份」題目和「課題」題目要梅花間竹,不斷循環。

詳情請參閱我的網誌,有關讀書技巧的文章。而專門講述「做 past paper 系統」的,只要點擊「past papers | 歷屆試題」這個標籤,就可以閱讀得到。


— Me@2013.03.20

2013.03.21 Thursday (c) All rights reserved by ACHK

Gödel’s speedup theorem

I only showed that the shortest proof of P(n) using Peano arithmetic is insanely long. I did provide a short proof of P(n). But I did this assuming Peano arithmetic is consistent!

So I didn’t give a short proof of P(n) using Peano arithmetic. I gave a short proof using Peano arithmetic plus the assumption that Peano arithmetic is consistent!

So, if we add to Peano arithmetic an extra axiom saying ‘Peano arithmetic is consistent’, infinitely many theorems get vastly shorter proofs!

This is often called Gödel’s speedup theorem.

— Insanely Long Proofs

— John Baez

2013.03.18 Monday ACHK

Noam Chomsky

Man: Mr. Chomsky, I’m wondering what specific qualifications you have to be able to speak all around the country about world affairs?

Noam: None whatsoever. I mean, the qualifications that I have to speak on world affairs are exactly the same ones Henry Kissinger has, and Walt Rostow has, or anybody in the Political Science Department, professional historians — none, none that you don’t have. The only difference is, I don’t pretend to have qualifications, nor do I pretend that qualifications are needed. I mean, if somebody were to ask me to give a talk on quantum physics, I’d refuse — because I don’t understand enough. But world affairs are trivial: there’s nothing in the social sciences or history or whatever that is beyond the intellectual capacities of an ordinary fifteen-year-old. You have to do a little work, you have to do some reading, you have to be able to think but there’s nothing deep — if there are any theories around that require some special kind of training to understand, then they’ve been kept a carefully guarded secret.

Compare mathematics and the political sciences — it’s quite striking. In mathematics, in physics, people are concerned with what you say, not with your certification. But in order to speak about social reality, you must have the proper credentials, particularly if you depart from the accepted framework of thinking. Generally speaking, it seems fair to say that the richer the intellectual substance of a field, the less there is a concern for credentials, and the greater is the concern for content. One might even argue that to deal with substantive issues in the ideological disciplines may be a dangerous thing, because these disciplines are not simply concerned with discovering and explaining the facts as they are; rather, they tend to present these facts and interpret them in a manner that conforms to certain ideological requirements, and to become dangerous to established interests if they do not do so.

— Noam Chomsky

2013.03.18 Monday ACHK