Judaism has changed and adapted over the course of time; polygamy, for example, is no longer allowed. So today is gay marriage something that Judaism should adapt to as well?

1. Judaism, the religion of the Written and Oral Torah, does and does not change over time. In geometry, we have a formula that states C = 2pr. As the value of “r” changes, so too does the value of C. The formula in Euclid’s plane geometry is eternal.
2. Polygamy is tolerated by the Torah and is not mandated by the Torah. In a world where women without husbands did not eat, polygamy may be understood if not accepted.
3. The male homosexual act is explicitly forbidden by Torah law. See Leviticus 20:13. There is zero debate on this matter in either the Written or Oral Torah regarding this rule.
4. The act is called toeva, seen by some as error, bNedarim 51a, and whatever an abomination actually means [derived sarcastically from wa’ab, the ancient Egyptian word for purity], the term applies to eating non-kosher food, [Dt 14:3], a woman who remarries a first husband after being married to a second husband, [Dt 24:4], bringing a disqualified offering to the altar, [Dt 17:1], and perhaps to the pernicious disposition of envy, as well. [Pr 3:32]
5. The Jewish marriage may take place between Jewish man who takes a Jewish woman in marriage. [Dt 22:13 and bQeddushin 2a] bQeddushin 82a reports that in Talmudic times, Jewry was not suspected of homosexual tendencies; in order to avoid rather than give license to sin, Rabbi Karo in Even ha-Ezer 24:1suggests that the assumption perhaps no longer applies and that men must be watched for sin as well.
6. Judaism always responds to the times, sometimes approvingly and sometimes not. Judaism has a discrete ethic which creates a sacred community and while aware of the outside world, sometimes rejects that world. At the “seder” of Plato’s aristocrats only by innovation Symposium, Socrates rejects the homosexual advances of Alcibiades, where “love” is discussed [and disgust!], whereas at the Jewish seder the poor are welcome, the behavior is chaste, and the topic for discussion is “redemption.”
7. In the condition of modernity, we can accept sinners but not sin. There are 613 commandments and not only one;   therefore communities may tolerate the sinner who does not upset public morality with provocative behavior. When asked to condemn homosexual behavior, Rabbi Ahron Soloveitchik is said to have said when asked about homosexuality, “it is almost as bad as cheating in business.”
8. As a religious minority, we advocate minority rights for others. We likely cannot change the homosexual community so we do not need to create animosity from it. We should better make our lifestyles more compellingly attractive. Monogamous heterosexual families seem to bond best, creating a more ethical culture on the whole. The promiscuity of our age is ultimately even more threatening. In an age of pluralism the homosexual community must also realize that there are those who view ethics differently than do they.
9. In conclusion, Judaism is opposed to the male homosexual marriage and defines marriage as [a] a man [b] initiating/taking a woman in marriage.

In the area of marriage Judaism has changed as well. Marriage until approximately 1000 C.E. was polygamous, although that was far more in theory than in practice for the last 1000 years of that period. In the year 996 C.E. an edict was issued among Ashkenazi Jews barring polygamous marriage. Although it was a 1000 year edict (and thus expired) it is considered a permanent edict. Sephardic Jews never faced such an edict (living amongst a polygamous Muslim majority as opposed to a monogamous Christian majority). Therefore when the mass influx of Sephardic Jews came to Israel in its early years, those married to multiple wives were ultimately permitted to keep the wives, but future generations were not permitted multiple wives.

 

Outside of polygamy marriage has changed as well. In the “old country” arranged marriage was the rule and often the bride and groom did not even meet until they were under the Chuppah (wedding canopy). Even among most communities that still use a shadchan (matchmaker) today, the young people are permitted to meet, date for a period of time and either accept or reject their prospective partner. Obviously outside of the traditional communities, Jews, like others in western society choose their mate based on romantic notions, not the financial and social considerations that usually determined arranged marriages.

 

Following this pattern, it seems that if Judaism accepts that people find their mates based on free choice and romantic attraction, then same-gender marriage falls into that category. The challenge, of course, are the texts in Leviticus that seem to clearly state that male-male intercourse is forbidden on penalty of death (18:20 bars the behavior, calling it an abomination – to’evah – and 20:13 where the death penalty is assigned). For many, this makes it clear that Judaism cannot tolerate such unions, but a closer reading of these texts make this much less clear.

 

First and foremost, there is no prohibition placed on women. While the Talmud includes prohibitions for lesbian behaviors, there is not rooting of this behavior in the biblical text. For male homosexuals, however, while the plain reading of the text may be discouraging, there is more than initially meets the eye.

 

The term used for intercourse is from the Root Sh-K-B – to lie with, which is used as a term for intercourse in the text primarily in situations involving promiscuity and/or rape, while the term yada is used for sexual relations in a marriage. This suggests that the prohibition is on those who either rape other men or do so in a promiscuous matter, often in the context of idolatrous worship during biblical times.

 

Additionally the term used to describe male-male intercourse is to’evah – abomination, and there are many, many prohibitions that take this title that Jews and others who oppose same gender marriage do not object to as strongly. Most commonly cited among these prohibitions that are to’evah is the ban on eating shellfish. Based on that one who is opposed to same gender marriage, in order to be consistent, would need to be equally opposed to opposite gender weddings that serve shrimp and lobster at the reception.

 

Therefore, among liberal Jews who do not take every commandment at face value, but rather delve deeper into the text and use modern methods of scholarship to derive meaning from the text, there should be no objection to same gender marriage. The definition, purpose and modes of creating a marriage have changed through the centuries, as the question suggests. Therefore, especially given the overwhelming evidence that same gender couples are capable of having the same type of stability and family structure as opposite gender couples, there is no reason for Judaism, most certainly in its modern forms, but also among the more traditional, should be opposed to same gender marriage.