MSPs were informed by Nicola Sturgeon that she intends to hold a second referendum about Scottish independence regardless of whether the UK government gives formal consent.
Ministers in the UK have already stated that they won't do this.
What arguments are there for or against another vote?
Holyrood has more MSPs who support an independence referendum than those who oppose it.
The Greens and the SNP won 72 of the remaining 129 seats.
Nicola Sturgeon described this majority, elected after making their indyref2 positions known, as a "cast iron democratic mandat".
She does not have the legal authority to vote on Scotland's relationship to the UK, in or outside of the 315-year old union.
This is because the law establishing the Scottish Parliament explicitly reserved the right to make decisions over this part of the UK constitution for Westminster.
This can make it more difficult and even more important to hold a referendum.
Some lawyers believe that Holyrood should have the right to hold a consultative vote because it would not be legally binding. Others argue that a Yes vote would weaken the union and create the expectation of change.
Judges would decide.
This tension was resolved through agreement between the UK and Scottish governments.
David Cameron, then the prime minister, accepted Alex Salmond as his first minister. He was given a mandate by voters to ask them if they wanted independence.
According to Oxford Languages, a mandate can be defined as "the authority to implement a policy given by the electorate to any party or candidate who wins the election".
Under a proportional voting system, Mr Salmond and his SNP won the majority of seats in the Scottish Parliament (69 out of 129), to ensure that no one party is dominant.
In their manifesto, the SNP promised a referendum.
Westminster temporarily transferred Holyrood's powers through what is known as a Section 30 order to allow MSPs the ability to legislate for referendums that were beyond legal challenge.
This was back then. Now, the political mood is quite different. This is not surprising, given that there was a referendum. It was described at the time by some as a "once-in-a-generation" decision.
Nicola Sturgeon, and other Yes supporters, repeated the "once in a lifetime" mantra throughout 2014.
Alex Salmond also explained to me that the gap of 17-18 years between the Scottish constitutional referendums of 1997, 1979 and 2014 was what he meant when he said "generation".
You can also argue that Brexit has fundamentally changed the context in which this proposition was made - that it is now overtaken and reaffirmed by events.
Boris Johnson, as prime minister, believes that now is not the right time to revisit the independence issue, given the Covid recovery and the cost of living crisis.
Nicola Sturgeon believes that doing so is crucial to allow Scotland to create its own recovery.
Although Alister Jack, the Scottish Secretary, has stated that any request for a new section 30 would be considered, he made it clear that "no" would be his answer.
He also dismissed the notion that refusing to cooperate with the UK government would mean denying democracy. He said, "I don’t accept that there’s a mandate at any time."
Mr Jack points out, however, that the SNP didn't win a majority at Holyrood by itself in 2011, unlike 2011. The Greens topped their total, leaving them one short.
Indyref2 opponents argue that the SNP, or the Yes side more generally, should win the majority of the votes.
Although the SNP, Greens, and Alba were successful in the regional ballot ballot in 2021, they were outperformed by pro-UK parties in the constituency vote in Scotland, where they consider it a mandate to resist indyref2.
Even the Scottish secretary suggested that a majority of electorate (not just those who vote) be required. This would be a high standard.
All this can be countered by the argument that the SNP/Greens now have more seats and vote than they did in 2011, and therefore their mandate is stronger.
Nicola Sturgeon accused those who don't accept this of being a "wrecking board" to the idea that the UK is a voluntary partnership.
Let's recap. To recap. This may seem absurd.
Chris Carman, a professor at Glasgow University in citizenship, said that there is no objective benchmark upon which to base mandate claims.
If strength of vote is important, Sir John Curtice, a professor at Strathclyde University in politics, argues that Nicola Sturgeon received "at least as strong and equally arguably as weak a mandate than the one Boris Johnson obtained in December 2019 to deliver Brexit".
This means that Yes parties received roughly the same percentage of vote in Holyrood's constituency ballot as Leave parties in the Westminster election in 2019.
Holyrood doesn't necessarily have the legal clout necessary to deliver on what Nicola Sturgeon promised.
According to the Scottish election study done after the 2021 Holyrood elections, a majority of voters in Scotland consider the outcome a mandate for Indyref2.
Even though it is clear that the SNP didn't win the majority of seats, this remains true.
Recent opinion polling indicates that there is not as much public demand for indyref2 to be held before 2023, as the Scottish government suggests.
Some suggest that a Canada-style Clarity Act should be passed to set out the democratic path to independence.
It is possible that the UK government may have a veto over the plans of the Scottish government for indyref2 without this or any other agreement.
Nicola Sturgeon is determined that this is not the case. She presented her plans for Tuesday's Holyrood referendum.
Boris Johnson might hope that the Scottish public will tire of constitutional politics and that independence questions fade in importance by sticking to his guns.
It is possible that resistance from the UK could increase support for independence to levels which are more difficult to resist. This is at most the goal of the indyref2 campaign, which Nicola Sturgeon started.
