"Gay marriage" is a concept made up of two terms. Those focusing only on the first half - whether in sympathy or hostility - ignore the essential part, which is the marriage.
That's because the struggle for gay marriage is also a struggle for marriage itself; for the life-long promise between two people to stick together, through thick and thin, in good times as in bad, until death parts them.
The root of this commitment is often love, but it also goes beyond love. The promise to stick together is founded in emotion but love alone cannot guarantee a marriage will work out.
By getting married, two people have decided on the future without being able to see into it. Nobody knows what he or she will feel for their partner twenty years down the line, but every bride or groom intends to still be with their spouses at that point.
And that is an undertaking based on work, respect, understanding, compromise and self-denial. Many people call these qualities conservative, or at least they fit well into a conservative worldview.
So its only surprising at first glance that it was a Conservative-led House of Commons that voted to allow same sex marriage in Britain.
Prime Minister David Cameron explicitly came out in support of the bill, which he said would make "society stronger."
Although Cameron's Tories were split on the issue, the Liberal Democrats and MPs from the opposition Labour Party voted almost unanimously in favour and the Marriage (Same Sex Couples) Bill was passed on Feb 5.
In Germany, where in place of gay marriage there is only registered civil partnership, a vote in the Bundestag lower house of parliament would see a similar result.
Across the western world, including in the United States, full acceptance of homosexuals is now the majority view. President Barack Obama supported gay marriage - and won re-election.
Whether in liberal Scandinavia or Catholic-influenced Spain and Portugal; South Africa, Canada, Iceland or Argentina, allowing same sex couples to marry is seen as a law of equality and emancipation.
Young people especially no longer care whether someone is straight or gay. While the fight against homophobia is not quite yet won, backward-looking ideologies are on the defensive.
Those old reflexes against gay marriage are not only anachronistic, they cling to tradition and seek to narrow horizons.
Instead of being glad that gay and lesbian couples want to venture into marriage, commit to one another and take responsibility for each other, these critics continue to put up redundant barriers.
The unfamiliar realm of same sex relationships, which are still perceived as threatening, obscures what is excellent about the institution of marriage.
Marriage gets particular protection under the German constitution, which has led to tax and pension laws favouring married couples.
The state promotes the marriage model and prefers it above other forms of relationships. For marriage is a also a relationship of liability and responsibility. In an ageing society the promise to stick together could quite easily last fifty or sixty years.
It's true that one third of all marriages in Germany fail. But that also means that two thirds stay together until the end. Marriage is alive and well and reports of commitment fears spreading in society are over-exaggerated.
Over 80 percent of all couples are married, despite increased mobility and changes in attitudes towards single life.
David Cameron has paved the way by saying, "I do" to gay marriage. Chancellor Angela Merkel should quickly follow suit.