Yes, he is concluding that (see BruceMcF's statement that Keynes worked with nominal GDP). But Keynes is very vague on the reasons why. The extended quote I gave is the entire argument as far as I can tell. So unless he developed it further in previous books, or it was "widely known" at the time that there were some problems (and what was the consensus back then?) it will be hard to figure out exactly what keynes had in mind.

We have met the enemy, and he is us — Pogo