Calling David Henderson, Tom Woods, Russ Roberts, and anyone else that thinks quoting one thing from Samuelson seals the Keynesian view of the post-war period....

I often reference the fact that in the very same book where Samuelson makes his dire predictions Alvin Hansen (the guy that's known as the "American Keynes"!) makes a positive prediction for the post-war period, with no fears about what the decline in government spending will do. I checked the book out last year, but I don't own it so I can't cite it at will. But anyone that does cite Samuelson clearly has the wherewithall to flip a few pages and get an equally authoritative Keynesian view (probably more authoritative back in the 1940s).

LK does do us the favor of quoting Hansen directly:

“The fact is that many people dread to think of what is coming. Businessmen, wage earners, white-collar employees, professional people, farmers—all alike expect and fear a postwar collapse: demobilization of armies, shutdowns in defense industries, unemployment, deflation, bankruptcy, hard times. Some are hoping for a postwar boom. We got that after the First World War. Not improbably we may get it again. If the war lasts several years, we may have at the end of the war sufficient accumulated shortages in residential housing, in durable consumers’ good such as automobiles, and in the plant and equipment required to supply peacetime consumption demands, to give us a vigorous private investment boom. Indeed, we need to be on the alert to prevent a possible postwar inflation. If in fact we do experience a strong postwar boom, there is, however, the gravest danger that it will lull us to sleep. Sooner or later such a boom will end in a depression unless we are prepared. If appropriate action is taken, there is no necessity for a postwar collapse.” (Hansen 1943: 12–13)."

And of course, there was a boom in private demand after the war, just as Hansen expected, and thanks to the success of Keynesianism among economists stabilization was an important policy concern in post-war America that economists were vigilant in thinking about, and we really didn't have major recessionary problems for quite some time.

And if "the American Keynes's" view of things isn't sufficient to stop people from spreading this misinformation, we can go to Keynes himself (also discussed by LK and also mentioned by myself here in the past). LK writes:

In 1943, Keynes was giving a lecture at the Federal Reserve and was asked by Abba Lerner about the possible economic problems of the post-war period. Keynes also predicted a post war boom:

“Keynes harshly rejected the risk of post-war stagnation, holding that because of Social security there would be a large reduction in private saving and so that would be no problem.” (Colander and Landreth 1996: 202).

What's more, Samuelson was aware that his pessimism was the minority view. He notes that in the chapter that Henderson, Woods, Roberts, and many others have made sure to quote from (they just don't quote that part). But what's even more remarkable is that Samuelson was so out of step with his fellow Keynesian economists that Harris - the editor of the volume - has an editor's note at the beginning drawing attention to the fact that this is just Samuelson's opinion, it's more pessimistic than most, etc. etc. Again, I don't have the book on me so if someone does and wants to share the language of the editor's note in the comments that would be great. If I recall, Hansen's positive chapter (that you never hear quoted) does not have the same sort of disclaimer from the editor.

The people who keep quoting Samuelson need to be able to explain why we should take Samuelson's pessimism as the final word of Keynesians in the 1940s when two giants like Keynes and Hansen held the alternative position before there is any more talk about this disproving the Keynesians.

If you think that Keynesians think you have to have lots of government spending to have a fully employed economy, you are confused.

You need demand, because although in the long run the economy is most definitely supply constrained, in the short run it is demand constrained.