What is the quote arguing? Does it still hold true today? Why or why not?

THOMAS JEFFERSON, LETTER TO GEORGE WYTHE
"I think by far the most important bill in our whole code is that for the diffusion of knowledge among the people. No other sure foundation can be devised,
for the preservation of freedom and happiness...Preach, my dear Sir, a crusade against ignorance; establish & improve the law for educating the common
people. Let our countrymen know that the people alone can protect us against these evils [tyranny, oppression, etc.) and that the tax which will be paid for
this purpose is not more than the thousandth part of what will be paid to kings, priests and nobles who will rise up among us if we leave the people in
ignorance." (August 13, 1786)