I object to the notion of unconditional basic income. I think the possibility of large portions of the population underachieving in their return to society while we are still not rich enough as society to afford it is very real. I'd propose a twist to this unconditionality. I'd much rather see a different brand of basic income in return for work that everyone can do in a relatively small number of hours per month (20h?-40h?).
In order to implement such a system we need a reliable way for society to judge the voluntary work of its members that would justify the basic income. And a set of works with social value offered to those whose chosen work is not deemed worthy of basic income.
I'll just try to make this more clear with a possible implementation of such a system.
You are allowed to receive your basic income and do whatever you want as long as a number of randomly selected people consider your work worthy of basic income.
A way to organise this would be to present what you have done in some kind of predefined format at the end of each year. These people decide if what you have done is worthy of you getting your basic income another year. Otherwise the next year you have to work in one of the state accepted ways to get your basic income (by teaching, playing with kids, cleaning the roads or whatever thing we as a society agree it's always worthy). To maximise the accountability I'd choose these random group of people in the community of the person who receives the basic income. They will have better ways to know wether what is presented is actually being done and worthy. These 'judges' would need to be anonymous to minimise the potential for social engineering to game the system.
This is just an example, I think we can devise different versions of the control structures following the same spirit for works that do not adjust well to this kind of evaluation.
Sorry for my grammar and english. Perhaps someone can restate this in a more readable way. English is not my first language and I'm not a great writer, but I hope at least the essence of the ideas behind this proposal pass through and can contribute to the general discussion.