Do you have anything to back this theory up? If our working time hasn't changed throughout the productivity gains during the 20th century there are other forces at play, namely political.
No. And I guess the same could be said for the opposite theory.
But just look around you: everything that is man made has taken an enormous amount of effort and accumulated knowledge. It's not been made by people who worked three hours per day devoting the rest to socialisation and a painting lessons. The people who invented antibiotics worked their asses off in university and laboratories to find a way for other people to survive infections. All the tools that they were using have been invented by people literally living in their shops and laboratories, and mass produced in factories, keeping their availability high and their price low.
If you take any situation or object in your life and follow backwards the chain of work and invention that has been needed to design it, produce it and keep it working, you realise that this chain has required an enormous amount of effort by everybody involved.
Sorry, I hadn't seen the second part of your comment.
Our working time hasn't changed throughout the enormous productivity gains of the 20th century. But the amount and quality of available products has. It's hugely superior.
Maybe you could work one hour per day in our present time and have the same products available that you had in the year 1900. But would you? Or would you end up asking someone to work just that one more hour when it's for a good cause - some life to save, some impressive machine to build, someone waiting in a queue, having fresh bread on Sundays or bringing you to some holiday destination in August?
My underlying point is that work is not an end in itself. Reducing coerced work, be it political, social or economical coercion, means more time to follow whatever passions one has, even if some of those passions may be things that you consider unproductive. For others, that extra time could mean another Einstein instead of a patent clerk with a less lenient boss than were the case.
