Consider this:
When the U.S. Constitution was drafted human beings were entirely capable of comprehensively understanding nearly every aspect of how the world around them worked.
How to grow food. Run a business. Understand emerging topics in science, math, philosophy and the arts. The optimism running through the renaissance thinkers is not surprising.
The drafters of the Constitution were masters of their world (to often unfortunately include slaves). They were confident in their direction moving into the future because they could predict the future --- based on their comprehensive knowledge of their present.
