Is avoiding tax immoral?
It repays reprinting a significant chunk of the Treasury chief secretrary's address to the Liberal Democrats' conference:
"Just as it is right to ensure that every benefit is fully justified, so we must ensure that every tax bill is paid in full. There are some people who believe that not paying their fair share of tax is a lifestyle choice that is socially acceptable. Just like the benefit cheats, they take the resources from those who need them most. Tax avoidance and evasion are unacceptable in the best of times but in today's times it is morally indefensible."
I am sure that many of you would agree with him. But "tax evasion" is illegal whereas "tax avoidance" is not: tax avoidance is the use of lawful devices to reduce taxable income and thus the tax payable to the Exchequer.
Now, there are plenty of individuals who see tax as just another of those irksome costs of doing business, such that they would be certifiable if they didn't do all that's necessary to shrink their tax bills. They would take the view that if they're not breaking the law in reducing the tax they pay on their income, then they're doing nothing wrong.
As it happens, a good number of donors to the Tories - Mr Alexander's partners in the coalition government - have engaged in what they would see as sensible mitigation of tax and what Mr Alexander might well see as hideous avoidance.
So I shall be interested to see the performance of the Tory chancellor, George Osborne, at the Conservative Party conference: will he use the same, tub-thumbing puritanical rhetoric in lambasting those who would rather pay substantial sums to specialist tax advisers, who minimise their tax bills, than hand that extra million or several to the public coffers?
Which shows, of course, that there is a very simple thing that the chancellor and chief secretary could do - at a stroke - to shrink the tax avoidance industry.
They could simply put a ban on giving public-sector work to any auditing, accountancy or consulting firm that has a tax advisory unit. Gosh, that would present the big four accounting firms with an intriguing dilemma.
All that said, quite a few business leaders and entrepreneurs would make a moral case for not paying tax: the less tax they pay, the more they're able to invest in job-creating opportunities in the UK, they would say.
In other words, there is a fine line between taking advantage of tax breaks explicitly created by the government to meet some kind of economic or social purpose and taking cynical steps to deprive the state of its due.
Would Danny Alexander, for example, take the view that most venture capital and private equity firms are behaving in a morally indefensible way, by financing their ventures with so much debt that interest payments wipe out most of their taxable profits and much of their corporation tax liability?
And what about the one man private-equity firm, Sir Philip Green, the owner of Top Shop, BHS and a fair chunk of the rest of the high street.
He would argue that the UK has benefited from the way that he's improved the efficiency of this substantial consumer-facing business - which is presumably why Mr Alexander and the government are using his talents to advise it on how to make the public sector more efficient.
But in 2005 Sir Philip saved himself around £300m in tax on a £1.2bn dividend from his main company, Arcadia - because Arcadia is registered as owned by his wife Tina, who is resident in the tax haven of Monaco.
Also the £1.2bn dividend was financed by increasing the indebtedness of Arcadia, which reduced the taxable profits of Arcadia and therefore the taxes that it pays (although Sir Philip has consistently argued that he chose not to load up Arcadia with as much debt as he might have done, so that he demonstrably pays more corporation tax than private-equity competitors).
None of that is a secret. And none of it is against the law.
But does Mr Alexander think that Sir Philip was engaging in laudable tax planning or showing a repugnant refusal to pay his way in the UK?
Where the line is drawn between acceptable and unacceptable tax behaviour is certainly not easy - but it is a big deal.
If a FTSE 100 company has a tax rate less than the headline rate of 28% is that evidence of an ethical crime against the state?
This would be quite something - in that most businesses, including the UK's largest public companies, believe they are letting down their owners, their shareholders, if they don't use and exploit every legal means to reduce the tax they pay.
In fact the advice to directors of public companies is quite clear: they are failing in their fiduciary duty if they allow their businesses to pay more tax than necessary. Which is why it is such a live issue in many boardrooms whether they should relocate the legal homes of their respective companies to countries where taxes are lower.
Perhaps Mr Alexander would direct his condemnation more against individuals who reduce their tax rate than against businesses. That's certainly the implication of the Treasury's announcement that it will endow Revenue and Customs' enforcement teams with an additional £900m of investment so that it can scrutinise the tax returns of the 150,000-odd individuals liable to the new top 50p rate of tax.
But at the upper end of the wealth and income scale - and Sir Philip Green is one of many cases in point - the distinction between individuals and businesses is a fuzzy one.
What Mr Alexander has done, of course, is to legitimise intensive media scrutiny of the tax practices of all Liberal Democrat and Tory MPs and of donors to their respective parties.
His colleagues in the administration won't thank him if hiring a tax accountant is today seen as embarrassing or shameful as having extra-marital affairs was in John Major's "back to basics" government.