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Posts published by “taidoka”

The Bible as Primary Source

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josephus headshot

Growing up in the Bible Belt meant that many of my friends didn't just believe that the Bible was divinely inspired, they believed it was literally true and argued - sometimes, strongly argued - that accepting the Bible as the infallible Word of God was absolutely necessary for salvation.

There's a great Christian word for that point of view: idolatry.

Biblical idolatry, to be specific: worshipping the Bible instead of Jesus. As I said when I started this series, Christianity is about following Jesus (faith), away from your old life (repentance), and towards the kingdom of heaven (goodness), in the hope of salvation (only accomplished by his sacrifice and grace).

Placing the Bible, a book - a collection of books, in three different languages, by dozens of authors, over centuries, collated by a completely different group of people - as the center of your religion is placing an thing - a divinely inspired thing, perhaps, but a thing - in place of Jesus God, and distorts Christianity.

Treating the Bible like a fax from God gets you so caught up in the buzzing of the machinery that you miss the message. People I respect get lost mining the minutiae of the Bible, combing through their  Interlinear Bibles to construct their own elaborate castles in the air in favor of simply following Jesus.

But how do you get to know Jesus if you don't know the Bible? You don't, full stop. Yes, you can - and should - read the Apostle's Creed, which summarizes what Christians have learned about Jesus, as approved by the descendants of his own apostles - who have evolved into our modern bishops.

But for us today - and even when the Apostle's Creed reached essentially its current form, 700 years after Jesus died - we must rely on the Bible to tell us who Jesus was. While the Church has traditions about Jesus not recorded in the Bible, even the Church itself doesn't consider these very reliable.

So we're stuck with the Bible to get to know Jesus - which is as it should be, scientifically (if you include history in the "sciences," writ large, which I do) because the New Testament of the Bible is the only extended primary source material we have about Jesus's life.

Before we drill into that, here's a question: Do you believe George Washington cut down a cherry tree?

If so, shame on your primary school history teachers, because it very likely didn't happen. The cherry tree myth was invented 7 years after George Washington's death - and almost 70 years after the alleged incident - by an early biographer, who didn't even include it until the book's fifth edition.

That doesn't mean it didn't happen - but if it had happened, it probably would have been mentioned in the writings of Washington or people who knew him. But the story was first told after everyone who could verify it was dead, by a biographer out to show Washington's success was due to his "Great Virtues."

Historians prefer not to use that kind of second-hand evidence (though, if all else is lacking, they'll grit their teeth and soldier on). They prefer to use primary sources - documents and diaries, art and artifacts, recordings and records that were directly created in the time of study, preferably by the people involved.

Put another way, if you want to know what George Washington thought, you need to look at what he actually said and did. Speculating about what he might have thought or did can be interesting, but unless that speculation can be tied back to actual documents about Washington ... you're just making it up.

In the same vein, students of the "historical Jesus" hunted for writings about Him by His contemporaries, and found only a handful: a few references in the historians Josephus and Tacitus written around AD 90 and AD 115, and just possibly some in the Talmud, collected around 200 from older oral traditions.

All these recount narratives that are brief and generally second- or third-hand. These primary sources let us know that Jesus existed. But if you want to know more about Jesus's life - whether you're a historian or a Christian or both - and you're looking for primary sources, the Bible is it.

We don't need to imagine that the Bible is an infallible fax from God in order to recognize we need to treat its words with utmost respect. If you wanted to learn what George Washington wrote in his diary, you wouldn't make a new diary entry up, now would you? The same is true of the Bible.

There are hundreds of manuscripts of the Old Testament and thousands of the New Testament, with many discrepancies; but this is where we start. I prefer the New Oxford Annotated Bible, others prefer the Interlinear; to help interpret them, I use histories like Ehrman's and Anglican and Catholic catechisms.

Jesus is God. Jesus lived as a human being. The Bible was written by human beings who were met and moved by Him, and was preserved by people who were following in His example of reading and sharing the Scriptures. We don't need to deify the Book; we need to look through it to the God behind it.

-the Centaur

Pictured: a primary source, in this case a 1st-century bust alleged to be Josephus, a historian born shortly after Jesus died, and who wrote about him while Jesus's contemporaries were still living. Whoa. Timing-wise, that'd be like ... like a picture of me in my 60's, if I had written a biography of JFK.

Coming Home

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This week has been so bad I feel like I'm under spiritual attack. It was supposed to be a vacation, but both my cats got sick, I got sick myself, and I had to work in the middle of it. I feel like the protagonist of a Neil Gaiman story I read in M is For Magic where a black cat is protecting a home from supernatural assault.

But now both of my cats are coming home. Gabby, the gold guy above, comes home tonight after a serious asthma attack, and Loki is already home after a serious urinary tract blockage.

Here's hoping two cats and prayers put things back on track.

-the Centaur

What is “Understanding”?

taidoka 1
When I was growing up - or at least when I was a young graduate student in a Schankian research lab - we were all focused on understanding: what did it mean, scientifically speaking, for a person to understand something, and could that be recreated on a computer? We all sort of knew it was what we'd call nowadays an ill-posed problem, but we had a good operational definition, or at least an operational counterexample: if a computer read a story and could not answer the questions that a typical human being could answer about that story, it didn't understand it at all. But there are at least two ways to define a word. What I'll call a practical definition is what a semanticist might call the denotation of a word: a narrow definition, one which you might find in a dictionary, which clearly specifies the meaning of the concept, like a bachelor being an unmarried man. What I'll call a philosophical definition, the connotations of a word, are the vast web of meanings around the core concept, the source of the fine sense of unrightness that one gets from describing Pope Francis as a bachelor, the nuances of meaning embedded in words that Socrates spent his time pulling out of people, before they went and killed him for being annoying. It's those connotations of "understanding" that made all us Schankians very leery of saying our computer programs fully "understood" anything, even as we were pursuing computer understanding as our primary research goal. I care a lot about understanding, deep understanding, because, frankly, I cannot effectively do my job of teaching robots to learn if I do not deeply understand robots, learning, computers, the machinery surrounding them, and the problem I want to solve; when I do not understand all of these things, I stumble in the dark, I make mistakes, and end up sad. And it's pursuing a deeper understanding about deep learning where I got a deeper insight into deep understanding. I was "deep reading" the Deep Learning book (a practice in which I read, or re-read, a book I've read, working out all the equations in advance before reading the derivations), in particular section 5.8.1 on Principal Components Analysis, and the authors made the same comment I'd just seen in the Hands-On Machine Learning book: "the mean of the samples must be zero prior to applying PCA." Wait, what? Why? I mean, thank you for telling me, I'll be sure to do that, but, like ... why? I didn't follow up on that question right away, because the authors also tossed off an offhand comment like, "XX is the unbiased sample covariance matrix associated with a sample x" and I'm like, what the hell, where did that come from? I had recently read the section on variance and covariance but had no idea why this would be associated with the transpose of the design matrix X multiplied by X itself. (In case you're new to machine learning, if x stands for an example input to a problem, say a list of the pixels of an image represented as a column of numbers, then the design matrix X is all the examples you have, but each example listed as a row. Perfectly not confusing? Great!) So, since I didn't understand why Var[x] = XX, I set out to prove it myself. (Carpenters say, measure twice, cut once, but they'd better have a heck of a lot of measuring and cutting under their belts - moreso, they'd better know when to cut and measure before they start working on your back porch, or you and they will have a bad time. Same with trying to teach robots to learn: it's more than just practice; if you don't know why something works, it will come back to bite you, sooner or later, so, dig in until you get it). And I quickly found that the "covariance matrix of a variable x" was a thing, and quickly started to intuit that the matrix multiplication would produce it. This is what I'd call surface level understanding: going forward from the definitions to obvious conclusions. I knew the definition of matrix multiplication, and I'd just re-read the definition of covariance matrices, so I could see these would fit together. But as I dug into the problem, it struck me: true understanding is more than just going forward from what you know: "The brain does much more than just recollect; it inter-compares, it synthesizes, it analyzes, it generates abstractions" - thank you, Carl Sagan. But this kind of understanding is a vast, ill-posed problem - meaning, a problem without a unique and unambiguous solution. But as I was continuing to dig through the problem, reading through the sections I'd just read on "sample estimators," I had a revelation. (Another aside: "sample estimators" use the data you have to predict data you don't, like estimating the height of males in North America from a random sample of guys across the country; "unbiased estimators" may be wrong but their errors are grouped around the true value). The formula for the unbiased sample estimator for the variance actually doesn't look quite the matrix transpose - but it depends on the unbiased estimator of sample mean. Suddenly, I felt that I understood why PCA data had to have a mean of 0. Not driving forward from known facts and connecting their inevitable conclusions, but driving backwards from known facts to hypothesize a connection which I could explore and see. I even briefly wrote a draft of the ideas behind this essay - then set out to prove what I thought I'd seen. Setting the mean of the samples to zero made the sample mean drop out of sample variance - and then the matrix multiplication formula dropped out. Then I knew I understood why PCA data had to have a mean of 0 - or how to rework PCA to deal with data which had a nonzero mean. This I'd call deep understanding: reasoning backwards from what we know to provide reasons for why things are the way they are. A recent book on science I read said that some regularities, like the length of the day, may be predictive, but other regularities, like the tides, cry out for explanation. And once you understand Newton's laws of motion and gravitation, the mystery of the tides is readily solved - the answer falls out of inertia, angular momentum, and gravitational gradients. With apologies to Larry Niven, of course a species that understands gravity will be able to predict tides. The brain does do more than just remember and predict to guide our next actions: it builds structures that help us understand the world on a deeper level, teasing out rules and regularities that help us not just plan, but strategize. Detective Benoit Blanc from the movie Knives Out claimed to "anticipate the terminus of gravity's rainbow" to help him solve crimes; realizing how gravity makes projectiles arc, using that to understand why the trajectory must be the observed parabola, and strolling to the target. So I'd argue that true understanding is not just forward-deriving inferences from known rules, but also backward-deriving causes that can explain behavior. And this means computing the inverse of whatever forward prediction matrix you have, which is a more difficult and challenging problem, because that matrix may have a well-defined inverse. So true understanding is indeed a deep and interesting problem! But, even if we teach our computers to understand this way ... I suspect that this won't exhaust what we need to understand about understanding. For example: the dictionary definitions I've looked up don't mention it, but the idea of seeking a root cause seems embedded in the word "under - standing" itself ... which makes me suspect that the other half of the word, standing, itself might hint at the stability, the reliability of the inferences we need to be able to make to truly understand anything. I don't think we've reached that level of understanding of understanding yet. -the Centaur Pictured: Me working on a problem in a bookstore. Probably not this one.

Work, Finish, Publish!

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So I think a lot about how to be a better scientist, and during my reading I found a sparkly little gem by one of the greatest experimentalists of all time, Michael Faraday. It's quoted in Analysis and Presentation of Experimental Results as above, but from Wikiquote we get the whole story:
"The secret is comprised in three words — Work, finish, publish." His well-known advice to the young William Crookes, who had asked him the secret of his success as a scientific investigator, as quoted in Michael Faraday (1874) by John Hall Gladstone, p. 123
Well said. The middle part often seems the hardest for many people, in my experience: it's all too easy to work on something without finishing it, or to rush to publish something before it's really ready. The hard part is pushing through all three in the right order with the appropriate level of effort. -the Centaur Pictured: Michael Faraday, Photograph by Maull & Polyblank. Credit: Wellcome Collection. CC BY.

The Sole Test of Any Idea

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Inspirational physicist Richard Feynman once said "the sole test of any idea is experiment." I prefer the formulation "the sole test of any idea open to observation is experiment," because opening our ideas to observation - rather than relying on just belief, instrumentation, or arguments - is often the hardest challenge in making progress on otherwise seemingly unresolvable problems. -the Centaur

Author Signing Now!

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Marriott, bottom floor, International Hall South. Follow the signs for the author signing, you can't miss it!