This afternoon MPs will "read" the Scotland Bill for a second time.


It's the first opportunity newly-elected Members, including many of "the 56", will have to debate the general principles of legislation quixotically intended to produce an "enduring settlement".

But the Scotland Bill Mark III (its predecessors having become Acts in 1998 and 2012) seems unlikely to represent third time lucky, for it's been overtaken by events, just as Mark II was in 2011.

And that the House of Commons is considering its second enhanced devolution settlement within five years highlights weaknesses on both sides of the constitutional divide.

From a Unionist perspective, the constant concession of further autonomy isn't just subject to the law of diminishing returns, but philosophically weak: if the central case for the Union rests upon further weakening that Union, then what exactly is the end game?

It risks, in other words, subjecting the Union to death by a thousand cuts. Only some sort of federal umbrella could make the Unionist offer more coherent, but although a more mainstream political aim than it was a few years ago, UK federalism remains ill defined and lacking in high-profile support.

Thus the driving force of the current Scotland Bill is altogether cruder: compelling the SNP and Scottish Government to put their fiscal levers where their leftish mouth has been for the past eight years. You want more generous welfare and a more equal society? Well, fine, here are the powers to make that happen.

Therefore it's no accident that the provisions of the 2012 Scotland Act - chiefly the ability to set a Scottish "rate" of income tax - will come into effect in April next year, just weeks before elections to the Scottish Parliament, enabling the Scottish Conservatives to offer a tax cut while simultaneously putting pressure on Finance Secretary John Swinney to set out his fiscal stall.

Last week my colleague Iain Macwhirter referred to this a "Tory trap", i.e. forcing the Scottish Government to mitigate the impact of further welfare cuts by raising taxes north of the border. He was right to identify such a cynical political calculation, but it only takes the counter argument so far.

Basically, the SNP appears to be saying (as it did over independence last year) that it wants a constitutional settlement from Westminster with no consequences, financial or otherwise, which simply isn't credible. Sure, the previous and present Scotland Acts will compel them to make difficult decisions but hey, guess what? So would independence.

In other words, there comes a point when the Scottish Government actually has to start pulling the "levers" it has been demanding for so long. And since 2007, they've actually been remarkably reluctant to do so, from the old "Scottish Variable Rate" (which the first SNP administration allowed to lapse) to many of the additional powers devolved under the Calman settlement.

The exception was Stamp Duty, which the Scottish Government made a point of scrapping and replacing with a more "progressive" system, although even that was quickly downgraded when it appeared middle-class Scots were going to take too big a hit, a reminder that "Middle Scotland" is much more important to the SNP's contemporary success than is often acknowledged.

Now the SNP usually explains its reluctance to use the powers it has on the basis that the accrued "benefit" (in terms of additional revenue) will flow to the Treasury rather than Edinburgh, and it's a reasonable point. But again, it only takes you so far: for pursued to its logical conclusion it's an argument against the Scottish Government doing anything to stimulate economic activity, and one assumes that isn't its aim.

Which brings me to full fiscal autonomy (FFA), or "responsibility" as the recent SNP manifesto preferred to call it. Here, too, the Scottish Government continues to tie itself in knots. Ministers strenuously deny rolling back on this commitment in the face of the falling oil price and unhelpful analysis from the Institute for Fiscal Studies, but it's difficult to reach any other conclusion.

Last week the SNP MP Pete Wishart downgraded FFA to an "aspiration", while the SNP's amendment to the Scotland Bill refers to the Scottish Government and Parliament becoming "responsible for all revenue raising" in the "medium term", which again begs the question of timescale. Independence, we were told, was deliverable by March next year, yet FFA continues to be kicked into the long grass.

In the interim, meanwhile, the SNP has two aims: "fully" implementing Smith and pursuing "early priorities" to enable "job creation", such as the minimum wage. As usual, however, this goal rarely progresses beyond platitudes and management speak, both much in evidence during the maiden speech of Michelle Thomson, the party's new Business, Innovation and Skills spokesperson. All the buzzwords were there: "growth" (as if no one else wants that), "job-creating powers" (left unspecified, apart from National Insurance) and even "happiness indices"; but no discussion, predictably, of the mechanisms by which a reduction in "inequality" would actually be achieved.

But then such has been the general tenor of Scottish political discourse for the past decade, endless demands for "more powers" but minimal discussion of how those extra powers would actually be used beyond vague generalities almost anyone, left, right or centre could sign up to. As is currently obvious from long overdue scrutiny of Scotland's educational record, constitutional visions have long trumped effective policy-making.

Nationalist strategists, meanwhile, are acutely aware of the political dilemma posed by the powers coming into force next April: if the Scottish Government chooses not to use the new "levers" at its disposal then its social democratic credentials will look rather shallow, while if it does, then the party risks losing Middle Scotland and therefore eroding support for the SNP and independence. In other words, it'll find itself between a rock and a hard place.

The last time the SNP actually proposed a tax increase was more than 16 years ago, the "Penny for Scotland" pledged at the first elections to the Scottish Parliament, and its perceived failure (i.e. losing votes) casts a long shadow over a supposedly centre-left party. In fact, since 1999 the party has consistently played down the importance of income tax as a fiscal lever, despite the fact it raises around a third of revenue.

So far Mr Swinney is hedging his bets, merely saying he'll "give consideration" to varying tax levels ahead of next year's Holyrood election, although it seems unlikely he'll go down that route. Instead I reckon he'll take the easy way out, i.e. continuing to depict his new powers as incomplete and unusable while claiming, when it comes to welfare, that a Westminster "veto" prevents ministers doing anything in that respect either.

But one suspects that this, like the Unionist parties' strategy, is subject to the law of diminishing returns. With greater power comes greater responsibility, and with greater responsibility come difficult choices. As Nigel Lawson once said, "to govern is to choose" and "to appear to be unable to choose is to appear to be unable to govern".