Here is the essence of this argument, as I see it:
A significant number of Scottish voters want to be independent of the political system called the UK. The political party committed to Scotland's independence, the SNP, was re-elected as the government of Scotland last May with a massive, decisive majority.
In that election campaign, the SNP made it clear that, if elected, they would call a referendum in the second half of the Parliamentary term, i.e. in the period November 2013 to May 2016. The indications have been probably mid-2014.
Only registered voters in Scotland at the time of the referendum, i.e. those on the voters roll, will be eligible to vote in that referendum. The referendum ballot paper will have a a YES/NO question on independence. It may have one or more other questions, e.g. a question on maximum devolved powers to Scotland while remaining in the UK.
The Scottish electorate understood clearly the position of the SNP on these matters and re-elected them with a decisive mandate to structure the referendum on this basis, including the number of questions, the formulation of questions and the timing of the referendum.
The referendum will determine the will of the Scottish people, and will either result in no action if there is a NO vote to the question or questions, or will deliver a mandate to the Scottish Government to negotiate with the UK Government, based on a YES vote to one or more questions.
The UK Government has already accepted that, although the referendum outcome is not regarded by them as constitutionally binding, they will accept it as the settled will of the Scottish people.
There are historical precedents for nations achieving their independence by various means, ranging from violent revolution and war (American independence), negotiated independence after a period of either violence or passive resistance (India and Pakistan) and velvet revolution, i.e. unilateral secession without violence (Slovenia).
Independence has never required the consent of both parties, only the determination of one party to leave a political union or empire. The details of the settlement may be negotiated, but the fact of independence depends not on law, treaty or contract but on the will of the people.