Comment by adwf

I think he's really talking about aristocracy/gentry whether he realises it or not.

Doubt is inherent in the process of intelligent reasoning. A highly intelligent person cannot come to correct conclusions about a topic without thoroughly examining it from as many sides as they can. They weigh up the pros and cons and then come to a conclusion. But even after all of that they will be aware of its flaws and downsides and thus doubt themself.

So why do I say aristocracy? Because the upper classes, the gentry and the wealthy were born into a position of power and confidence. Just because of who they were in society, they believed they were right. And as they were wealthy, they also made up the vast majority of scientists/philosophers/etc. The downfall of the aristocracy throughout the 19th and early 20th centuries led to the new thinkers no longer having that inbuilt "born-to-rule" mindset, that while arrogant, also lent an arrogant confidence to their position that a common intelligent man may not have.

In short, it's not confidence that led the thinkers of old to undoubting - it's arrogance. And maybe a little bit of that is always necessary to get things done...