Marriage is a contract. The popular idea of marriage, however, is that it is the result of two people meeting and falling in love. Marriage is the consummation not only of this, but because families become involved in the relationship. And though the couples are aware of this, I believe they tend to think of the marriage as theirs alone. The couples I've known are so happy to have found each other, they might be only dimly aware of their families--until they're planning the wedding. It's unusual for many couples, given the right tax bracket, to be aware they're becoming part of an institution that is financial in nature and regulated by the government. That taxes reward those who marry, though, ought to make clear the government's position about marriage. It's not just this; institutions are structured so that there are just over one thousand benefits that accrue to married partners, many of them financial.
Currently, which couples can marry is much debated. One faction declares that marriage is ordained by the Bible. It is to be between one man and one woman. Rick Warren, a Christian fundamentalist, has said that marriage between one man and one woman only has been universal for 5000 years. I don't know where he gets this figure. Not only is this historically and egregiously inaccurate, the Bible, in fact, condones marriage with numerous wives. Mistresses are frequently discussed and clearly acceptable. (Solomon had a thousand wives and mistresses.1st Kings and Nehemiah.) The Bible condones gang rape (Lot offered his two virgin daughters to an angry mob to prevent them from attacking his guests. He said they could '...do what you like with them' but to leave his guests alone 'for they have come under the protection of my roof' Genesis 19). That guests who were strangers to him (elsewhere mentioned) were under the protection of his roof, while his daugnters were not, somehow horrifies me more than anything else here written about. Fathers can sell their daughters as sex slaves (Exodus 21). The Bible condones incest. (Abraham is married to his half-sister, Sarah. Lot's two daughters have sex with him.) Lastly, the Bible is sometimes against marriage; it admonishes not only those who would consider marriage, it is against any relationship of a sexual nature ('It is good for a man not to marry' 1st Corinthians, 7. And 'He who does not marry, does even better' 1st Corinthians, 7). The Bible is nothing if not inconsistent. I no longer own one, though I once had nearly memorized it. I'm sorry I can't be more specific about Biblical chapter and verse.
On the other side of the argument, there are those who assert that marriage between adults of the same gender is also, in fact, truly marriage, and should be legally and socially recognized as such. They wish it were celebrated as are other marriages and, in fact, it's known that family recognition and support of the marriage is beneficial. Because marriage for same gendered couples has not been an option, some have already started families, either biologically or through adoption. Various studies, conducted independently and usually by universities, have concluded that children of same sex marriages and families function as well as, or slightly better than, the children of hetersexual parents.
Inherent in most ideas are premises, assumptions, and conclusions of one sort or another. For example, in the idea that marriage should be legally available to couples of the same gender is the premise that within societal institutions, separate but equal is neither practical nor possible; that which is separate is never equal. With the adoption of the 14th Amendment to the Constitution in 1868, this idea became law. With the 1954 Supreme Court decision Brown vs The Board Of Education, the idea was further developed. Separation always negates parity, it makes impossible equality, though everything else might correspond: "Where a State has undertaken to provide an opportunity,...such an opportunity is a right which must be made available to all on equal terms" (Brown vs Board Of Education, 1954).
Beyond ideas, or in addition to them, are facts. One example having to do with homosexuality is the biologist who has documented consistent homosexual behavior in over 450 species of animals. He's not alone; other biologists are now publishing the same results from their research in the field. I've seen both photographs and videos of this behavior on the part of animals.
And beyond ideas, and facts, there are opinion and emotion and all sorts of things, like, perhaps, work. Which I have to get back to. And that's a fact.