Answer:
Personally, for a few sentence summary, I would say:
“The author feels as if current means of discovery lack soundness and that the true way of discovery is, so far, unknown or untried. He appears to wish to go off more scientific knowledge and proven facts with less ‘fantastical’ beliefs that are ‘ill-defined.’”
I believe it was directed towards an adult audience, specifically an adult audience with a longing to learn and discover instead of accepting these tales, of sorts, as truth. I hope this helped. I tried to comprehend it, but I do live in 2020, not 1620, haha. Good luck!