Through most of history knowledge was esoteric. In Ancient Egypt only a select few were chosen to be scribes, and among them were the physicians. The physicians must have the ability to read because, after about 2,700 B.C., much medical wisdom was shared from one generation to the next by texts written on Papyrus.
The priests, physicians, and especially the rulers, monarchy, of the ancient societies must have feared the common folks gaining access to knowledge. For this reason few had access to books Even if these few had access they had no means of learning to read it. Hence, most people were kept illiterate on purpose. Only people with a need were educated. This made it easy to brainwash a populace into believing whatever was necessary for society to function.
A good example of this occurred in 213 B.C. in China and is referred to as the "burning of the books." Shi Huang (246-210) founded the Qin Dynasty in 221 B.C. He wanted to create an empire that was united, and he wanted to create what he referred to as an ideal society. In order to do this he ordered the burning of all books with the exception of books dealing with medical care, astrology and agriculture. He also ordered 460 literati (educated people) to be burned alive. The goal was to eliminate any knowledge of the previous Confucian governments, or Confucian knowledge. He wanted to assure no one has knowledge or desire to oppose him.
As we should be aware by our study of history, similar attempts to keep people ignorant occurred in Nazi Germany and Communist Russia. It occurs to some degree today in China and other nations that want to keep their people ignorant to prevent any attempt or desire to oppose the government, king, or totalitarian dictatorship.
Even in America we see some attempts to keep the masses ignorant. Many of our schools fail to adequately teach history with the hopes of changing it to what they want. The progressives have been doing this since the 1960s. It was done in the 1960s and 70s with the Fairness Doctrine that attempted to force radio stations to show both political points. There are attempts today by political groups who want to shut up opposing view. This is seen by liberal groups who want to shut up Rush Limbaugh and Fox News.
In my view, one of the greatest and most important documents in the history of the world was when the founding fathers added in the 2nd amendment the freedom of speech. This was the first time ever that people were allowed protective freedom to speak out against their government. They were allowed to be educated, even if that education showed the current administration was lying or untrue or simply wrong.
The Chinese in 213 did not want any criticism of the government. The U.S. Constitution assured that people were allowed to speak out against the government without being punished. However, this same freedom is not shared among institutions, whereby if you talk bad about the place you work, or about your boss, you may be fired (the modern version of being killed).