Can you be certain that the sun will rise tomorrow? It will. It rose today, it rose yesterday, and the day before that. And before that. I saw it. Dawn will break tomorrow. Ah, but that's today, and yesterday. And yes, you observed the sun in the sky. But what guarantee does that give you that it will break through the clouds tomorrow? Mathematical logic doesn't require that the sun break in the east. Or breaks at all. And your senses have no evidence that it will rise on Friday, only that it sprung from the sea on Thursday. But of course it will. Of course the sun will rise. You're probably right. But logically, you can't know it for certain, that's my point.
David Hume's Enquiry Concerning Human Understanding can be a disturbing tract. Those ideas of cause and effect you take for granted, that the sun will rise tomorrow, that the impact of one billiard-ball will dislodge and move another? These aren't necessary conclusions of deductive reasoning, but are at best provisional, probable judgements based on your experiences. There are no guarantees. This is usually referred to as the idea (and sometimes, as the problem) of induction. The bottom line: we've got to be pragmatic, and make our best guesses, appealing to our experiences and judgements, and live as if we knew the sun would come up tomorrow. Hume's observations about probability aren't limited to physical examples, but extend to predictions about folk too:
"A man who at noon leaves his purse full of gold on the pavement at Charing Cross, may as well expect that it will fly away like a feather, as that he will find it untouched an hour after. Above one half of human reasonings contain inferences of a similar nature, attended with more or less degrees of certainty proportioned to our experience of the usual conduct of mankind in such particular situations."
Certainty seems much on political vogue at the moment. Demands for rain-or-shine predictions of the future are a staple of the constitutional debate. In yesterday's debate in Holyrood, critics of the SNP government's equal marriage proposals harped on the same string. Sure, Mr Neil, you've written all of these safeguards for religious bodies and people in your Bill, but where are the guarantees these protections won't be subject to legal challenge and fail?
Law-making in Scotland today is subject to complex and often unpredictable pressures. This is nothing new. The Scottish Parliament isn't sovereign. Holyrood may legislate across great swathes of territory, but is bound to observe the limits of the devolution settlement, Convention rights and European Union law. Constructing the scope of Holyrood's powers under the Scotland Act isn't always straightforward and predictable. The debatable legality of the independence referendum before the section 30 order was passed being an excellent case in point.
European Union law is also, in many respects, open to interpretation, leaving the door ajar for legal challenges to the parliament's decisions. We saw - and see - this writ large, in the imminent challenges to the legality of the SNP's flagship minimum price for alcohol policy. For the Scottish Government, the proposals do not represent an unlawful restraint on the single European market, but a policy intervention justified on grounds of public health, whose intervention in the single market is reasonably proportional to the end sought. The tobacco giants Sinclair Collis and Imperial Tobacco used similar legal arguments, unsuccessfully to challenge the Scottish ban on cigarette vending machines in court.
And as those of you who have ever attempted to read a decision of the European Court of Human Rights will know, human rights law isn't a bumper book of easily implemented rules either. Despite popular perceptions to the contrary, law is rarely so determinate or straightforward, but applying the Convention can be particularly tricky. Courts have to ask, does the law engage a protected right? Does the government measure pursue a legitimate aim? Does the measure strike a fair balance between the protection of rights and of the public interest?
Opponents cited Convention rights to challenge the fox hunting ban early in the life of the Parliament. In 2012, we saw AXA and other big insurers try to rely on property protections under Article 1 of Protocol 1 to challenge the legality of the Holyrood legislation which confirmed that pleural plaques arising as a result of exposure to asbestos represented an actionable personal injury in Scots law. AXA lost in the UK Supreme Court.
So what's the lesson of all of this? Is it, as John Mason, Richard Lyle and Elaine Smith suggested in yesterday's same-sex marriage debate, that parliament should tremble at the mere possibility of legal challenges, and decline to enact the Bill? Should it do so in every circumstance, or just here? Ought Holyrood not to have banned cigarette machines, allowed foxes to be hunted down and torn to bits by dogs, declined to offer a remedy to those who have been negligently exposed to asbestos - or have attempted to introduce the independence referendum - for fear of a committed litigant, who might attempt, however unsuccessfully, to challenge the law?
Because that committed litigant is invariably lying in wait, whatever the legal measure you're discussing, dreaming up ways to shape the flexible legal material of EU and ECHR law into an arguable case to put before the court. That's the nature of the beast. That's always Holyrood's basic predicament when making laws. To demand certainty where achieving cast-iron certainty is impossible, and then to cite that uncertainty as grounds not to pass this legislation, is cowardice, wrapped up in quibble and constitutional illiteracy. It is to take the worst possible lesson from Hume's philosophy. If there is no reassurance which could possibly persuade you, no reasonable prediction based on good evidence which you would accept, you're beyond talking to.
If you don't want to endorse same-sex marriage because you feel Yahweh's burning gaze on your back, of because you feel the Natural Law demands it, by all means say so, and vote so. As a Godless tyke, I can't sympathise much with Roseanna Cunningham's explanation for her No vote yesterday, but characteristically, Roseanna gives you her reasons bluntly, without legal pettifogging. That's creditable, in its way. But the hyperventilated fears expressed by Mason, Lyle and Smith yesterday are not. The SNP MSP Marco Biagi put it best yesterday:
"Above all, we must not be drawn by the remote and hypothetical challenge to religious freedom to such an extent that we overlook the very tangible, very real and very much on-going violation of personal freedom that is the exclusion of people of same-sex attraction from expressing their love through marriage, which is the institution that our society considers to be the paragon of commitment."