Replacing yourself with a very small shell script

March 26, 2012

One of the professors this semester gave me substantial liberty to design some of the homework assignments, liberty that I am now beginning to rethink.

The students have written programs implementing various alignment algorithms, which I grade automatically with a script that runs a bunch of unit tests and reports the results. Sometimes, though, the tests fail, and I must wade into the source to figure out what happened. If you ever want to ruin a nice weekend, try reading twenty different people’s perl code back to back.

I mentioned this to my fiancee’s father. His reply: “I’ve been using perl for twenty years, and I still learn something new every time I use it. That’s a problem.”


On a somewhat disappointing correspondence

March 24, 2012

I recall reading in Wittgenstein somewhere (Notes on Certainty?) of his fear of insanity: isn’t it possible, he asked, that one could be insane without knowing it? While Wittgenstein may have been right in point of fact to doubt his sanity (the state of his own mental health was often unclear), the general point seems underappreciated to me. We sometimes experience disagreements so bewildering that we may even be unable to locate the source of the disagreement. Such encounters leave us wondering whether the other parties to the epistemic conflict are really sane at all. By symmetry, shouldn’t we extend that doubt to ourselves?

(Attention conservation notice: long, boring, internet drama, arguably with no moral to the story)

Read the rest of this entry »

The Straussian impulse in homework

March 19, 2012

This semester I’m TA’ing for the upper level bioinformatics course.  As far as teaching assignments go, it’s really ideal: it’s my intended area of specialization, I get to work for wonderful professors and I’m afforded considerable latitude in teaching and assignment-writing.  (The latter two points were also true of cell bio last semester, though the first was definitely not.)  The bioinformatics course is unusual in that attracts both biology and computer science majors, roughly at a ratio of 1:2.  As such, there is considerable diversity in the students’ academic backgrounds, and it is expected that students will sometimes have knowledge of subjects (e.g. algorithms or biochemistry) that exceeds what is required for the course.

I think this may explain an annoying tendency in the graded assignments that I have noticed for some time but haven’t been able to put my finger on.

This tendency, which is probably more common among the CS kids than the biologists, is to lend obscure, esoteric interpretations to questions and answer them accordingly.  Mostly these involve pedantic or legalistic readings of questions which seem pretty facially straightforward to me.  For example, a warm-up question might ask for the output of an algorithm expressed in pseudo-code which prints the limiting ratio of F(n+1)/F(n), where F(n) is the nth Fibonacci number.  The facially straightforward answer to this question is 1.618… or phi, which most of the biologists were able to identify.  The legalistic, “gotcha” answer is 1, because division could be interpreted as C-style integer division.

But there is absolutely no reason to think that C-sytle semantics for the division operator were intended in the first place!  The behavior of the division operator in C was motivated by concerns of machine efficiency in general, and closure over ints specifically.  It’s not an especially important or universal fact about computer science, and there’s no reason to assume it’s implied in pseudo-code.  It actually requires “reading against the grain” of the assignment, which asked the student to identify the ratio in the next question.  Worse, the CS students know that they’re taking an interdisciplinary course where C’s division semantics is not common knowledge.

Nevertheless, the bureaucratic interpretation was depressingly common among CS students.  I would write it off as an isolated incident or a “thinko”, except that such mis-interpretations reccur with depressing regularity.  My pleas to adopt commonsensical readings of homework questions do not make a difference.

Why does this approach to homework bother me so much?  It assumes that there is an obvious interpretation of the assignment fit for commoners, and an esoteric interpretation of the text intended only for readers equipped with rare learning and subtle powers of discernment.  In other words, my students are Straussians about homework.

Ruth Barcan Marcus (1921-2012)

February 20, 2012

Sad news from Leiter that Ruth Barcan Marcus has died. I was lucky to meet Marcus once very briefly, and I described this encounter at Feminist Philosophers in a comment that a moderator suggested I repost (edited slightly for clarity):

Always sad to hear, although she led a very long and influential life. I hope it’s not out of place to share a memory, even if it’s slightly goofy.

As undergraduates, a friend and I skipped classes for the better part of a week to take a road trip to APA Central in Chicago in 2006. I was thrilled to find out that Ruth Barcan Marcus was in attendance, since I was studying her work in modal logic at the time. Her presence practically commanded every session she attended, and I think it was clear that she no longer cared a whit what others thought. I remember her developing a cough during one talk, rising without a word and inching her way down the aisle until she reached the speaker’s podium, pouring herself a glass of water from the pitcher using the speaker’s glass, drinking it while the flustered speaker attempted to continue, then returning slowly to her seat. It wasn’t an unreasonable thing to do, but it’s something that very few people would even have considered, and struck me as very bold but also very funny.

She never hesitated to spar, sometimes brusquely, with philosophers perhaps a third her age. I think her hearing was perhaps beginning to give way by then, and she spoke in a kind of 90dB monotone bark. At one point she asked a speaker to explain the so-and-so theory. The speaker launched into a vigorous defense of the so-and-so theory until Marcus cut him short: “I DON’T WANT TO DEBATE IT, I JUST WANT TO KNOW WHAT THE THEORY IS!” (Who among us can truly claim the guts to say that at a conference?) Even now, six years later, when my friends and I talk philosophy and one of us feels like we are getting snowed over, we quote Marcus at the offender.

It probably took me until the second or third day to work up the courage to ask her a question, since I was a lowly undergraduate and she, one of my living philosophical heroes. I asked her something about the logical omniscience of chickens, which unleashed a scouring attack of Dennett’s view on the matter (this had been the topic of a previous session). I barely remember the rest of the conversation, since I was struggling not to pass out from sheer awe, but getting the honor to debate the logical omniscience of chickens with Ruth Barcan Marcus was my favorite memory of that conference or any other.

Her faculties were razor-honed even at the end of her career, and the persona of queen regnant of logic that she seemed to inhabit was somehow both terrifying and charming. It must sound hyperbolic, but meeting her in person was absolutely thrilling, and remains with me now as one of my fondest memories of that time.

Intelligent Mechanics

February 15, 2012

It’s odd that the fundamentalist reaction to modern science is primarily confined to evolutionary biology. No preachers ever go after the conservation of energy, which is presumably a much larger obstacle to God’s active hand in the world.

On Examples

January 12, 2012

It’s important to give examples, but difficult to give good ones. I’m thinking primarily of the use of examples in computer science, where one can often feel tension over the issue of realism. In an expositive discussion of an algorithm, for example, a “realistic” input will usually be too large, too specific or too incidentally structured to serve a didactic purpose. On the other hand, toy examples can be counter-productive in the sense that they obscure the original motivation for the algorithm: if you have ever endured a “class Square extends Rectangle” lecture, you have felt this. Good examples negotiate these two poles and almost whisper to the reader “but you see how this generalizes…”

There is almost a sense of poignancy in shallow examples given by an author who understands their subject deeply, and there is a class of reader (including myself at times) who is liable to mistake that poignancy for condescension. Perhaps it would be better taken to
consider them as a sort of technical koan. The author admits: “I cannot foresee all of the situations in which this concept will be useful to you, yet I must pick something.”

As an aside, this sentiment seems related to a sort of meta-problem in the arts that probably has something to do with the topics of genre, idiom, and at one step removed, the Bloomean anxiety of influence. The artist knows that the audience has seen that brush stroke, read that phrase, heard that chord before. Yet the artist must do something.

The importance of examples was impressed upon me recently as I was rereading Minsky’s <i>Society of Mind</i>. I had picked it up years ago at a
free bookstore, but was put off by what struck me as an almost patronizing presentation of the subject matter. Rereading now, the examples are less cutesy, the tone more earnest, and the aim more radical than I remembered. There is something humbling in reading Minsky discussing a child playing with blocks, not because he doubts you are up for anything more complex, but because he thought it the best vehicle for the concept at hand.


August 10, 2011

It’s time to go to sleep when compiler errors start sounding like good ideas for t shirts.