Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?
Stern stuff. The Old Testament also endorses polygamy.
So giving credence to anything proposed by the religious or social conservatives risks a similar if different ‘slippery slope’ argument. “Traditional Marriage Paves The Way For A Return To Polygamy”.
This is a reminder that it is in the very nature of our political system that laws may be changed, and that any change to any law means that it could be further reformed in the future. This is not a bad thing (although those who see their values falling out of fashion tend to see it as such).
Are there any immutable laws that are not open to revision by future parliaments? In times past, God’s Law performed this function. But this was a flawed system, not least because religious authorities seem happy to re-legislate the Word of God when it is convenient. Countries with a written constitution seek to encode some underlying laws that frame what legislators can and cannot do… but constitutions are open to amendment and repeal. In Britain, the European Convention on Human Rights can trump domestic law. Its incarnation in British law, the Human Rights Act, has a certain meta-status, governing what other laws can or cannot say. But even these laws are open to repeal or withdrawal by law-makers.
There is no final arbiter that can prevent the slippery slope towards mad laws, dangerous and unethical laws, if a parliament wishes such things to be so. This is why the vigilance of the people is so important – to ensure that the law keeps pace with, but does not go beyond, our values. This seems to be happening in the case of the Marriage (Same Sex Couples) Bill, which reflects the new public consensus that marriage should be available to all.