My problems were the things everyone complained about ... and what you're complaining about, too. I agree with you that it seemed to undermine the entire point of HDM: that this world, the things we can sense and understand, the experiences we seek out that spark emotions and knowledge and learning in us, the things we can change with our own abilities and understanding and a lifetime of hard, intentional, purposeful work, is what matters, and we should strive to live a meaningful life within it. 'We must build the Republic of Heaven where we are,' and all that. I think what he meant with the 'secret commonwealth' was stories and the imagination, and how powerful those can be in service of a life well lived in the physical world, but it was a very garbled message, and lost a lot in the execution. That's the most charitable explanation I can give.