Society for the Diffusion of Useful Ignorance

I quite enjoy this excerpt from Henry David Thoreau's essay Walking from The Portable Thoreau

We have heard of a Society for the Diffusion of Useful Knowledge. It is said that knowledge is power, and the like. Methinks there is equal need of a Society for the Diffusion of Useful Ignorance, what we will call Beautiful Knowledge, a knowledge useful in a higher sense: for what is most of our boasted so-called knowledge but a conceit that we know something, which robs us of the advantage of our actual ignorance?
What we call knowledge is often our positive ignorance; ignorance our negative knowledge. By long years of patient industry and reading of the newspapers-for what are the libraries of science but files of newspapers?-a man accumulates a myriad facts, lays them up in his memory, and then when in some spring of his life he saunters abroad into the Great Fields of thought, he, as it were, goes to grass like a horse and leaves all his hardness behind in the stable.
I would say to the Society for the Diffusion of Useful Knowledge, sometimes,go to grass. You have eaten hay long enough. The spring has come with it's green crop. The very cows are driven to their country pastures before the end of may; though I have heard of one unnatural farmer who kept his cow in the barn and fed her on hay all the year round. So, frequently, the Society for the Diffusion of Useful Knowledge treats it's cattle.
A man's ignorance sometimes is not only useful but beautiful-while his knowledge, so called, is oftentimes worse than useless, besides being ugly.
Which is the best man to deal with-he who knows nothing about a subject, and, what is extremely rare, knows that he knows nothing, or he who really knows something about it but thinks that he knows it all?