The Score on Marriage (including Gay Marriage) [Last Modified on 2006.12.03]
Marriage is much more a secular institution than a religious one; despite what the Religious Right would have us think, having a religious ceremony has no true meaning because that alone will not grant you the rights, benefits and privileges of marriage that the government grants — whereas getting a legal marriage license confers those rights upon you and any marriage partners. Each religion is free to make its own rules surrounding what kinds of marriage ceremonies it will or will not perform and recognize, but the government must recognize any type of marriage and convey the same overarching rights and privileges to any married persons, regardless of their choice of partner(s).
The upshot is that marriage must be a simple legal contract like any other, a sort of "incorporation" of the married parties as a single entity with regards to certain laws (rights, benefits, privileges and responsibilities). The government will (as it already does) recognize this contract as an agreement between the parties, and will confer the appropriate rights to the matrimonial entity.
No individuals interested in entering into a marriage contract can or should be prevented from doing so. This means that, as with any other such contract, the government who grants the rights conferred by the contract cannot discriminate on the basis of race (which it used to), sex (which it still does), religion, or any other factor beyond the interested individuals being human beings (because a clear line can be drawn at species) and of legal age to enter into binding contracts. This also includes the number of individuals interested in entering into a marriage contract — while polygamy or polyandry may be objectionable to other parties, such an arrangement is up to the consenting (and legally independent) individuals who wish to enter into it.
The only arguments against gay marriage — or pluralistic marriage — are religious or intolerant in nature; the government has no right to endorse the former, and has the responsibility to refrain from endorsing the latter.
The bible has no place in the laws of this country, or its states. We don't govern based on religious texts or beliefs — the Constitution is the law of the land. That said, Judeo-Christians like to claim that the bible contains a singular definition of marriage as a loving union between one man and one woman. In fact, there are eight different "definitions" of marital relationships in the bible, such as the standard "nuclear family," polygynist marriage (one man, many wives), levirate marriage ("inheriting" your brother's wife), and the practice of keeping concubines. Many of the bible's rules and examples of "proper" marriage amount to nothing more than sanctioned serial rape. The bible says nothing at all about homosexual marriage (its authors simply didn't think of the possibility).
The "definition" of marriage is a ridiculous notion, since language is a living entity, which evolves and changes over time to adapt to the society in which it is spoken. The Christian church itself did not recognize marriage as a sacrament until the twelfth century.
The uncomfortable truth of the matter is that neo-conservatives are attempting to revert society in general — and the practice of marriage specifically — back to their Rockwellian ideal, a pristine (and unrealistic) world where a man and a woman (and only a man and a woman) get married, have 2.4 children, and never divorce (no matter what). This ambition reveals a remarkable lack of adaptability and understanding, and a highly tenuous grasp on the realities of change, development, and civil rights in our society. We wouldn't presume to declare — but we certainly have a hunch — that these neo-conservatives have no problem with the inevitable setbacks which would result from such a reversion; such as the loss of women's rights, since as far as the bible is concerned, they're property, and the Rockwellian 1950's barely raised this status.