No to polygamy

One of the spurious arguments that religious conservatives have circulated in their desperation to prevent another Western country allowing same-sex marriage is that it will lead to legalised ­polygamy or incestuous marriage ­(your report, 28 September).

This argument maintains that if homosexual couples are ­allowed to marry on the mere grounds that they claim to love each other, then any relationship based on avowals of love would logically have to be allowed.

When homosexual couples marry, they do not do so on the mere grounds that they claim to love each other. Other conditions which apply to heterosexual couples apply equally to them – namely, that they have no ­existing spouses and no blood ties closer than cousinship.

These last two conditions are not eradicated by removing the opposite gender rule.

Any proposal to remove them would have to be considered, and any good reasons to prohibit polygamy and incestuous marriage will still be good reasons when same-sex marriage is allowed.

I challenge anyone to think of good reasons for these two prohibitions which would be invalidated by same-sex marriage. The inability of a couple to procreate has never been a reason to disallow marriage, which is why old and infertile people can marry.

Robert Canning

Scottish Secular Society

Broughton Street

Edinburgh