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With the same-sex marriage law coming into effect with the first ceremonies in England and Wales on Saturday, who are those that oppose it and what are their reasons?

Sometimes the debate on gay marriage has been polarised, casting those who supported the measure as the right-thinking and those who opposed it as irrational and guilty of tacit homophobia.

The law to allow gay marriage passed quickly and there are those who still feel they have not had a proper chance to air their concerns.

1. The religious sceptic

There are religious people who oppose gay marriage primarily out of a fear that one day equality laws will force a church, mosque or temple to host a ceremony.

Religious institutions have been protected from this scenario under the so-called "quadruple lock". The law will ensure no discrimination claim can be brought against religious organisations or individual ministers for refusing to marry a couple. But there are some who just don't believe in the quadruple lock.

"It's flimsy," says Fiona O'Reilly, of Catholic Voices. "At the end of the day we are subject to the European courts and they may see things differently.

"Where the vast majority of same-sex couples don't want to force religious institutions to marry them, what is clear is that there's a small minority who basically say that true equality should force places of worship, and that's what they then start to seek. These safeguards can get eroded and 10 years down the line they may not mean as much."

There's also religious opposition about the redefinition of the traditional understanding of marriage.

"Marriage is a unique kind of relationship that involves a man and a woman and their ability to create new life in the form of children," says O'Reilly. "The church isn't looking to impose its understanding of marriage on others, but it is looking for its understanding of marriage to be protected."

2. The historical meaning case

But there are not just religious objections to changing the definition of marriage.

Definition of marriage The OED currently defines marriage as: "The condition of being a husband or wife; the relation between persons married to each other; matrimony"

It also adds that "the term is now sometimes used with reference to long-term relationships between partners of the same sex"

The previous definition was: "A formal union of a man and a woman, typically as recognised by law, by which they become husband and wife"

"Same-sex relationships differ from heterosexual ones in ways that can't be changed by legislation," says philosopher Brenda Almond, who argues that the primary historical and traditional function of marriage is procreative.

"The main reason for the state to be involved with marriage is children," says Prof David Paton, an industrial economics lecturer at the University of Nottingham and a supporter of the Coalition for Marriage, a group arguing that traditional marriage is beneficial to society and would be undermined by a definitional change. "It seems reasonable for the state to treat the one type of relationship from which children can directly result in a different way to others, and this is the basis for marriage laws," says Paton.

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Not all marriages will result in children, he concedes, and also suggests that issues such as pension rules or inheritance may require the state to recognise alternative relationships in different ways.

But the same-sex marriage law is not about this, he says. "It's about changing the very definition of marriage to encompass other types of relationships that are inherently different. That is both unnecessary and carries the risk of weakening the legal structure designed to encourage the attachment of children to their natural mother and father."

3. Not all gay people are in favour

Not every gay person is in favour of gay marriage. Some are against it. "I am a Conservative and a homosexual, and I oppose gay marriage," wrote the Daily Mail's Andrew Pierce in 2012. "Am I a bigot?"

Historian David Starkey, has also said he is unconvinced. "I am torn. As an atheist gay who regards marriage as part of the baggage of heterosexual society which I have come to respect but can never fully share, I am tempted to say a plague on both your houses," he wrote in the Daily Telegraph in 2012.

Image copyright Getty Images Image caption The historian David Starkey: "I'm torn on gay marriage"

Actor Rupert Everett perhaps gave the most colourful argument against, in a 2012 interview in the Guardian. "I loathe heterosexual weddings. The wedding cake, the party, the champagne, the inevitable divorce two years later. It's just a waste of time in the heterosexual world, and in the homosexual world I find it personally beyond tragic that we want to ape this institution that is so clearly a disaster."

4. Civil partnerships are there so is change just about terminology?

There are some who argue that the difference between marriage and civil partnerships is primarily a semantic one. "We've got marriage, it's called a civil partnership and I rejoice in the fact that people like me who are different from straight people can do something they can't. I relish that," Pierce said last year.

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Others say any remaining differences between civil partnerships and marriage could have been amended through existing legislation.

"Society gave legal and institutional expression to what many hold to be true - that gay and lesbian people should have the same rights to formalise their commitment to each other and enjoy the social and legal benefits that opposite-sex couples have," said the Lord Bishop of Exeter to the House of Lords in 2013.

"If there are matters in that legal provision that are inadequate or missing, rights that have not been conferred or legitimate aspirations not recognised, then that act should be amended, and that would have my general support."

"In legal terms it's virtually no different from civil partnership," says Labour MP Ben Bradshaw, who formed his own civil partnership in 2006. But he counters that he's in favour of the gay marriage law because it is a necessary symbolic and cultural step towards full equality.

5. A question of a rushed law

For some the main issue is the passage of the law itself. When the bill was discussed in the House of Lords, ex-chief constable Lord Dear tabled a "wrecking" amendment attempting to block its progress. "I have no problem at all with homosexual marriage or partnerships," says Dear. In his view civil partnerships are too much like getting a driving licence and deserve a sense of dignity and occasion.

"My problem was, and still is, that the government didn't give it enough thought and didn't go through the processes they should have done for something as sensitive and important as this," he says. It was rushed through parliament with "indecent haste", he says, without a royal commission, an in-depth inquiry, or any mention in the manifesto.

"What I was saying was to take it away, do it again and bring it back." A bit like a pedantic headmaster, says Dear. "Then it's all on the table so you can see exactly how you pick your way through the minefield.

"As it is I think we're going to have to put sticking plaster all over it for years to come."

Correction: A quote by Fiona O'Reilly has been removed that implied that the Catholic Church for England and Wales accepted the passing of the law on civil partnerships, which, in fact, the church opposed.

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