However, the actor declined to comment on his own persuasion on the issue for "career preservation".
"This is the first time in years a developed country has talked about splitting up and it’s a massive thing," he said.
"If you vote for a president or a prime minister based on political or economic issues and they don’t deliver, that’s not so bad – you can protest four years down the line and vote them out. If you vote for continued unification or independence there is no protest vote – that’s it. And that could be it for decades, for centuries. There’s no going back from it."
He added that his decision was a "matter of the heart and a matter of personal identity and national identity", rather than based on economic reasons. The referendum will take place on 18 September.
"If we vote and it doesn’t work out, am I going to look back and think ‘I voted because I thought I’d be a bit better off or I was going to get some oil, or did I vote because I believe in Scottish identity and Scottish independence’?" he said in an interview with the Huffington Post.
"That’s way more important than the political or economic arguments because they change daily. Independence or unification is here to stay forever. For me, they don’t marry."
Numerous high-profile names have added their vote to the much-publicised debate. Among those arguing for independence are Frankie Boyle, The Proclaimers, Alan Cumming, Billy Bragg, Sean Connery and Annie Lennox.
The list of those who want Scotland to stay within the union include JK Rowling, David Bowie, Eddie Izzard, Alex Ferguson, Mike Myers and Emma Thompson.
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