Earlier quoted context omitted.
On the other hand, those 5 million additional people probably aren't going to sit around doing nothing. That's not how human nature works, either - most people are happier doing something rather than nothing! Self actualization and all that. This is really the core assumption behind Marxism; perhaps not so much the sclerotic centrally-planned dictatorship of the proletariat 'Marxism' we saw in the 20th century as the…
Un-monetized self-motivation is not required, here. They would be have the opportunity to earn above and beyond the basic income. It's not Marxist or communal at all. We are not talking about abolishing work for pay. We are simply talking about an un-earned payment in addition to whatever they earn in conventional jobs.
On the other hand, those 5 million additional people probably aren't going to sit around doing nothing. That's not how human nature works, either - most people are happier doing something rather than nothing! Self actualization and all that.
I don't think that it's completely relevant to the BI debate, but what if everyone actually did just decide to sit around doing nothing?