Did he actually suffer from imposter syndrome, or was he being humorously humble?

I can really understand why such great minds could have imposter syndrome. They put so much thoughts and work into their findings, and stumble upon so many obstacles, struggling for months or years to make it work, to finally reach a result that makes so much sense and eventually seems simple to them. In the end, they just think anyone with the same dedication, work and curiosity could have done it, and that they actually took quite some time to figure it out, and that the theory is actually imperfect and could be better, and the only reason they did it is because of some random hindsight anybody could have had...

What they forget is that their journey has only been possible by a combination of intuition, skills, dedication and raw intelligence that together form a genius other people just don't have. But they do have a point in the fact that people probably underestimate the amount of work and struggle necessary to reach their results. Imposter syndrome is when you think you put too time and work to realize how logic a series of deductions is, while most of those are actually clever and their accumulations put you light-years ahead of those wouldn't didn't make them, for whom it's just magic.

If you read his biography by Walter Issacson, he was considered fairly mediocre for many years in his youth and quite heavily internalized it.

Yeah I think it's the latter.

Don't be so sure. Einstein, in spite of all his achievements, was human. He made mistakes and misunderstood some things. Overall he understood physics more deeply that any of his time, but from his point of view maybe it came so naturally that he never felt he had totally "earned" his recognition. That said, he was known for humility, but that doesn't mean it was disingenuous.

Isn't that the point of "impostor syndrome"? No matter where you stand, your measurement of your ability is subjective to whatever standards you personally hold, which may be different from an objective assessment? And maybe there is no true objectivity? Maybe it's all... relative?

Einstein already made his most significant contributions by age 26 and spent the rest of his life arguing against quantum theory, the dominant school of the 20th century. Most modern physicists regard the latter portion of his life a waste in way of contributions.

That’s a little misleading — the latter period started around age 40. E.g. Bose-Einstein statistics was from 1918, which would be age 39 if 1905 was 26. The EPR paper was many years later still. Also, you can’t leave general relativity out of his most significant work.

Honestly, I could understand why. Einstein is regarded as one of the best scientists in history, when there are so many other great scientists. He might have been a genius, but even he would question whether he was the best, especially since he did most of his best work at an early age.

Neil Armstrong also apparently suffered from imposter syndrome:

http://journal.neilgaiman.com/2017/05/the-neil-story-with-ad...

As a plagiarist he had to suffer. Don't tell me you have no clue what I am talking about.

He probably wasn't at all. https://www.quora.com/Was-Einstein-a-fake-and-a-plagiarist

I didn't know that there was an accusation because we was Jewish. I meant that he was plagiarist and it has nothing to do with his origins and beliefs.

Would you mind elaborating or giving a source for that?