Sunday, March 30, 2014

The Religiosity of Bigfoot Believers

According to a Gallup survey of over 1700 random people, approximately 17% of the U.S. population believes that creatures such as Bigfoot and the Loch Ness Monster will eventually be discovered by science. Belief in Bigfoot is an interesting way to look at religion, because it is essentially independent of any religious teachings. Bigfoot isn't supernatural. People generally don't believe in Bigfoot because of their religion, and they don't choose their religion according to their belief in Bigfoot.

Compared to people who don't believe in Bigfoot (who I'll call "non-believers"), Bigfoot believers tend to have slightly lower income, slightly less education, and slightly more liberal political ideology, but the differences are fairly small. As one would expect, people who believe in Bigfoot (blue bars) are much more likely than Bigfoot non-believers (tan bars) to believe in a wide variety of things, including some that are supernatural.

Thus, one might also expect that Bigfoot believers would be more likely to believe in God and to be more religious in general. That's partly true. 91% of Bigfoot believers believe in God, compared to 87% of Bigfoot non-believers. They also are slightly more likely to believe in Heaven, Hell, angels, demons, and that Jesus is the Son of God. However, according to a wide variety of metrics, Bigfoot believers are substantially less religiously devout than Bigfoot non-believers.

Despite being slightly more likely to believe that God exists and that Jesus is his son, Bigfoot believers are substantially less likely to identify as Bible believing, born again, evangelical, and fundamentalist than people who don't believe in Bigfoot. They attend religious services, religious education, and prayer meetings less often. They also pray and read religious texts substantially less often than people who don't believe in Bigfoot.

Some people say that religious people are religious because they are gullible and willing to believe things for which there is no compelling scientific evidence. Whether that's true or not may depend on whether Bigfoot is real.

Sunday, March 16, 2014

The Gospel According to a Map

Has the messiah come? Christians say yes, and they usually use the gospels to "prove" it, showing that Jesus fulfilled messianic prophecies. But many of those were about relatively minor details (e.g., where he'd be born) that could've been fabricated by the gospel writers. There were, however, much bigger messianic prophecies, and we can verify them without using holy books of any religion.

Back around 730 BC, God's people were divided: Israel in the north, Judah in the south. Israel was recently conquered and exiled by Assyria, and Judah was headed toward a similar fate via Babylon. Only a few people in Judah believed in God, even fewer in Israel, and practically nobody in the rest of the world. Other nations didn't care about Israel's God, because each one had its own gods. Israel and Judah were reviled and were essentially irrelevant in the world.

The prophet Isaiah offered hope to his people by telling them a king ("messiah") would come and establish a "kingdom" of unprecedented size and strength. Other nations would become followers of Israel's messiah and he would be a moral authority to them (Isa. 2:3). Through him, "the earth would be filled with the knowledge of Israel's God, as the waters cover the sea" (Isa. 11:9). Similar predictions were echoed by other prophets over the next couple centuries, but to no avail. Jerusalem was destroyed in 586 BC and its people exiled. The region was later conquered by Cyrus (Persians) in 539, Alexander the Great (Greeks) in 332, and finally by Pompey (Romans) in 63 BC. It probably seemed like the biblical prophecies would never be fulfilled.

Over 2000 years later, the world looks a lot different. Most of the popular gods of the ancient world (e.g., Baal, Dagon, El, Molech, Asherah, Osiris, Isis, Chemosh, Hadad, Artemis, Zeus, and Caesar) are no longer worshipped. Others are mostly confined to particular regions. But there is one glaring exception. According to polls by Pew Research, the majority of people in the world (55%, including 81% outside of China & India) are, at least nominally, followers of the God of Israel. The following map shows countries (in blue) where the majority of the adult population professes Judaism, Christianity, or Islam as their religion.

As someone who makes over 600,000 weather predictions every day, I know well that correct predictions aren't necessarily evidence of divine revelation. But I also know that consistently accurate predictions always are based on analysis of past data, accurate assessment of current conditions and/or recent trends, a correct understanding of how the universe works, or some combination thereof. These explain how meteorologists can make (somewhat) accurate predictions of future weather, futurists and science fiction writers can predict future inventions, and political analysts can (sometimes) predict the next president. But they don't explain the messianic prophecies.

There is nothing to suggest that the unprecedented events that were prophesied were logical inferences from the available data at the time. Quite the contrary! The data pointed much more toward Israel and Judah being destroyed like most of their neighbors and their God ending up like Baal, Chemosh, Asherah, and the others, as minor footnotes in history.

We don't need to take the Bible's word for it. These are well-attested historical facts, as is the fact that the prophetic books were written long before Jesus was born. It's possible that the messianic prophecies were extremely lucky guesses. Verification of them is not proof of messiahship or divine revelation, and parts of them have not yet been completely fulfilled. But if "evidence" means a body of facts that is more probable if the hypothesis is true than if it is not true, I consider it strong evidence.

Saturday, March 8, 2014

Interpreting the Hebrew Bible with Artificial Intelligence

I often hear the question "Do you interpret the Bible literally or figuratively?" The answer is "both" and "neither", mostly "neither". The Bible contains different genres of writing, which should be interpreted accordingly. They include history, prophecy, poetry/songs, stories, and wisdom literature, to name just a few. Identifying the genre is important, but it can be very subjective. It's also difficult without understanding the original language. Those problems can be solved with machine learning.

I developed an algorithm to interpret the Bible in its original language. I started by writing a Perl script that parses the BHS Hebrew text, removes vowel points, and identifies every word used at least 50 times in the Bible. I also removed stop words (i.e., common irrelevant words such as ani [I], at/atah [you], mah [what], etc.). Keep in mind that in Hebrew some articles & prepositions are prefixes rather than distinct words (e.g., "land" = aretz, "the land" = haaretz, "in the land" = bearetz). The final list included 560 Hebrew words. I calculated the relative frequency of each word (i.e., how often the word is used compared to the other 559 words), then standardized the values. The result was 560 numeric variables, each representing a sufficiently common and sufficiently relevant Hebrew word.

560 variables is too many to easily work with, so I used Principal Component Analysis to reduce it to a few manageable variables, each of which was a linear combination of the standardized relative frequencies of all 560 words. To understand what the principal components mean, I plotted chapters of books of the Bible with obvious/known genres: History (e.g., 1 & 2 Chronicles), Prophesy (e.g., Isaiah), and Wisdom Literature (e.g., Proverbs). Each dot on the graph represents a chapter where the genre of the book (though not necessarily of the chapter) is known.

The first two principal components do an excellent job of separating the books of different genres! The first (PC1) seems to indicate how historical vs. poetic it is. The lowest value (-14.8) is for 2 Chronicles 27, a very historical chapter detailing the reign of king Jotham. The highest value (4.5) is for Psalm 21, a very poetic song. PC2 measures another dimension that (at least in theory) is not related to how historical/poetic a book is. It does a great job of distinguishing between prophecy and wisdom literature. The big outlier among the prophetic books (red triangle on the left side of the blue cluster, at PC1=-9.3, PC2=0.9) happens to be Jeremiah 52, which is a very historical chapter despite being in a prophetic book.

PC1 and PC2 also were calculated for entire books and for chapters/books of unknown genres. Those can be plotted on the same graph to visualize how similar they are to the known genres. For example:

For a more quantitative genre classification, I built a Logistic Regression model using the first 6 principal components. The model estimates the probability that a writing belongs to one of the three broad genres, assuming those are the only three options. As an example, I applied it to each chapter of Genesis and plotted the output below:

According to the model, the first, 3rd, and 15th chapters are by far the least historical, which might disappoint some who interpret Genesis 1 as a scientific or historical narrative. The biggest outlier, however, is chapter 15, which the model thought was very likely prophetic. Indeed, Chapter 15 is about God's covenant with Abram and includes several prophecies about the future.

K-Means Clusters, Hebrew Bible
Classification into these broad genres is only the beginning. If other genres, writing styles, authors, topics, etc. can be identified, another model could easily be built to classify writings according to those, using the same principal components calculated here. If none of those things are known, Cluster analysis can be used to identify writings that have various features in common (see example on the right).

My plan (if I ever get enough free time) is to set up a web page where anyone can easily get the classification values for each chapter of each book. We may never get to a point where computers and algorithms can accurately interpret the Bible for us, but they certainly can be helpful.

Saturday, March 1, 2014

Confirmation Bias: The Bible on Gay Marriage

My favorite desert was the Sahara
When I was about 7 years old I loved deserts. I loved them so much that I wanted to make my own. I found a patch of dirt in the front yard, planted a cactus there, and called it my desert. I wanted to prove that it was a real desert. I knew deserts were hot, so I took a little key chain thermometer, put it in my desert, and left it there for a while in direct sunlight. The thermometer said 120 degrees (F), which would've been a new all-time record high for San Jose, California. I was so excited! I knew it felt more like 80 degrees, and I kinda knew that thermometers aren't supposed to be placed in direct sunlight, but it didn't matter. I had proof that my desert was a real desert!

As a child, I had already mastered confirmation bias. Confirmation bias is the tendency to seek out and accept evidence that confirms what we already believe or want to believe, and reject evidence that contradicts those beliefs. It's so powerful that when participants in controlled experiments are given fabricated evidence (unknown to them that it's fake) specifically designed to disprove their beliefs, they interpret it as actually supporting their beliefs. Bible interpretation is rife with confirmation bias. One example is the debate over same-sex marriage.

Many opponents of gay marriage point to commandments like Leviticus 18:22 & 20:13, which say a man should not "lie" with a man as one would with a woman, as proof that homosexuality is wrong and thus gay marriage should be illegal. Some mention the fact that God created humans male and female and suggest that God defines marriage as between one man and one woman.

Bible-believing proponents of gay marriage have found convenient ways around biblical commandments, such as pointing out commandments against wearing clothes of different fabrics and planting fields with different seeds (both in Leviticus 19) or about eating certain foods like shellfish. Others find support for gay marriage in the words of Jesus. Some even suggest the close relationship between David and Jonathan was more than just friendship.

All of these are examples of overfitting and confirmation bias, which often reinforce each other. People have strong opinions about homosexuality and gay marriage for cultural reasons. That was true before the Bible was written. Currently, the best predictor of one's opinion about gay marriage is age. According to recent polls, 70% of Americans aged 18-29 support it, compared to only 41% who are 65 and older. Even the majority of Republicans aged 18-29 support gay marriage, a higher percentage than Democrats aged 65+. At least half of young evangelical Christians also support same-sex marriage, similar to older non-religious people.

As a strong supporter of gay marriage, I'll inevitably be accused of confirmation bias here, which I can't deny. Nevertheless, I'll try my best to avoid it while answering some common questions.

What does the Bible say about gay marriage?
Nothing. Gay marriage wasn't an issue when/where the Bible was written, so it wasn't directly addressed. 

What does the Bible say about homosexuality?
Specifically, nothing. The prohibitions in Leviticus are of a very specific act, one that should not be equated with homosexuality or even practicing homosexuality. Those prohibitions had a very practical purpose at the time (i.e., longevity in the new land), as stated in the same chapters. Whether they still apply is debatable, but it's a different debate. Other mentions of same-sex activity in the Bible involve rape or prostitution, which are similarly condemned for heterosexuals. Even if the Bible did teach that homosexuality is wrong, that has never been the standard for legislation. Idolatry and blasphemy, for example, are clearly wrong according to the Bible, but almost nobody sees the First Amendment as an attack on biblical morality. 

What about fabrics, seeds, and shellfish?
In my opinion, this is a bad and unnecessary argument for same-sex marriage. There's a major difference between these and the commandments given in Leviticus 18 & 20. Leviticus 18 was directed at both Israelites and foreigners (Lev. 18:26), but the next chapter (the one that prohibits different fabrics and seeds) was directed only at Israelites (Lev. 19:1), as were the dietary laws. This is an important distinction to Jews, who generally believe that non-Jews are only required to follow the 7 Laws of Noah, which include sexual immorality (Lev. 18) because it also applied to "foreigners", but not the ceremonial and dietary laws or those in Lev. 19. A similar belief was evident among early Christians (see Acts 15). 

Does the Bible define marriage exclusively as one man and one woman?
No. Biblical marriage often was between one man and multiple women. Among the many examples are Abraham, Jacob, David, and probably even Moses. Rather than condemning it, the Bible gives provisions for how to treat multiple wives (e.g., do not neglect your first wife after you get another one; Ex. 21:10). Ironically, some Bible-believers argue that gay marriage is a slippery slope that could lead to legalization of polygamy, perhaps forgetting that the Bible allowed it.

Gay marriage is a controversial political and cultural issue. As much as we'd like the Bible to settle all of our political and cultural debates, its authors had a different purpose. That doesn't mean the Bible is irrelevant or that everything is morally neutral unless there's a specific commandment against it. But we need to be very careful to allow the text to speak for itself rather than using it to confirm our own beliefs. The Bible doesn't give direct commandments about everything, but it does give one (also in Leviticus) that summarizes all of them: "love your neighbor has yourself." That one sometimes is forgotten by people on both sides of the gay marriage debate.