UBI is not so attractive that most people will choose to do nothing with their lives. UBI is intended to keep people from starving, but it's not a very pleasant life, devoid of comforts and aspirations. Sure, there will be people who want that, but there will be many others who don't.

The most important tool there is a good education, which is mandatory for even the children of the laziest and most shiftless. That's where they get exposed to the possibilities of what they could do, and be engaged by. They'll be presented with role models in the form of teachers, who do get up and do work every day, and live better lives because of it.

Maybe they'll create nothing more than pointless forms of art. But even so, what would be wrong with that? Movies and video games are both pointless idleness, but they create genuine joy, and there were lots of mis-steps as people learned what forms of them would be worth doing. Similarly, a lot of the most advanced science seemed like navel-gazing until it turned into transistors and lasers and GPS.

I don't mean to be blandly utopian. There are many ways UBI can fail, and we will probably do all of them in varying experiments. But neither would I be so dystopian about people doing nothing at all with their lives. People enjoy comforts and they enjoy having purpose. Between the way our existing technology creates more than enough food and shelter at little cost, and the desire of many people to improve their lot in ways that also continue to move society forward, I think we can afford to experiment with letting some people live lives of complete (but unenviable) idleness.

I'm sorry but 1), 2) and 3) are ridiculous. What are you basing those assumptions on ? I don't see how any of these points relate to UBI. Why would we be obligated to provide welfare to people who spend their allowance on things other than food and healthcare ?

4) is a very good point. We don't actually know what keeps our civilization running. UBI assumes that people have a natural drive to be productive, but we got to where we are in a context of natural selection, survival instincts and greed. Removing those aspects from society is rightfully scary.

I'm also worried about inflation. If you give everyone $X/month to spend on essentials but the supply of those essentials doesn't change, then a very likely outcome is that the price of essentials, in aggregate, will go up by $X/month.

We already see some of this with student loans. The government decided that education is important, so it created federally-backed student loans that anyone can apply for, and effectively increased the amount of money available for education by a large amount. Some of this did go into increasing the number of kids that could go to college, but much of it just went into increasing the price of education. Plus, the supply of good jobs didn't really go up by much, so all those extra kids who went to college are now fighting over the same jobs they would've gotten in the first place, just with crushing debt burdens.

Most people will want to do something useful to supplement their basic income because it will only be enough to pay for the basic necessities. Would you want to live like a poor student for the rest of your life, renting a bedroom and being only able to afford thrift shop clothes and ramen noodles? Most people aspire to have their own place, date other people, have friends, etc. Most people have some minimum amount of drive for status. That will ensure that they make some effort to rise above the bare minimum.

As for how to pay for this, consider that central banks have printed trillions of dollars and basically handed that money to corporations, bailing them out of their debt. We live in the world of corporate welfare. We could expand the money supply and give that money to the people instead. In some ways, this is more capitalist than the alternative. Why? Because corporations who get too far into debt should die. If you give money to the people, you at least ensure that corporations will have to sell people something that they actually need/want, instead of being able to count on a corporate bailout.