Orwell created "Newspeak," a language that "grows smaller every year" (67) and whose overt purpose is to remove the nuance of language. For example, the word "good" has an "Oldspeak" antonym "bad"--as Syme argues--but "bad" has nuances that made it an inexactly opposite of "good." If you're trying to simplify a language, nuances are problematic. Why not use "ungood" or "doubleungood" instead? The ideas are simpler, there are fewer words to learn, and the nuances of meaning are erased.
Syme, Winston's enthusiastic colleague, explains one of Orwell's main points about the power of language:
‘Don’t you see that the whole aim of Newspeak is to narrow the range of thought? In the end we shall make thoughtcrime literally impossible, because there will be no words in which to express it. Every concept that can ever be needed, will be expressed by exactly one word, with its meaning rigidly defined and all its subsidiary meanings rubbed out and forgotten. Already, in the Eleventh Edition, we’re not far from that point. But the process will still be continuing long after you and I are dead. Every year fewer and fewer words, and the range of consciousness always a little smaller.'
In other words, when the range of one's vocabulary is limited, the range of one's ability to think is limited in direct proportion. The goal of the Ministry of Truth is to utterly control the people, and they understand that ideas are dangerous. To alleviate that problem, they are changing language itself, eliminating any words that aren't black and white, any words with nuance. By doing so, they are slowly changing the ability of the masses to think beyond the realm of simple "good" and "bad."
Syme goes on to say:
'How could you have a slogan like ‘freedom is slavery’ when the concept of freedom has been abolished? The whole climate of thought will be different. In fact there will be no thought, as we understand it now. Orthodoxy means not thinking—not needing to think. Orthodoxy is unconsciousness.’
This is the ultimate goal of the Ministry of Truth: unquestioning compliance (of the masses) in all things, because in the end, the people will lack the ability to think in any meaningful way.
Orwell, being a master of language himself, understood this truth on a visceral level. If you'd like to experiment with it to better understand it, choose someone with a far more limited vocabulary than you have--like a child--and try to explain a complex idea, like home mortgages. You'll find that you have to oversimplify until you aren't really explaining the concept at all; you're merely grazing the top of it. The child will walk away understanding little more than the fact that you have to keep paying a lot of money for so many years that it seems like forever to live in your house.
Orwell's observation is also clear when we realize that all languages tend to adopt words from other languages. This usually doesn't happen when they have their own idea of a concept, but when the other culture conceives of the idea and makes a word for it. For example, the German word schadenfreude means to take pleasure in the misfortunes of others; it's a distinctly German concept--at least, it originated that way--and the we adopted the word when we adopted the idea. Words are the vehicles of thought, and as we expand our vocabularies, we correspondingly expand our abilities to think more expansively.
We do the same thing with history, incidentally. For well over a century, American schoolchildren have been taught an oversimplified and biased (toward patriotism) form of history that produces unquestioning, patriotic young men and women--patriotic, quite often, because they have not been taught the truth of their nation's history. They have been systematically given only the truths (and sometimes outright lies) that served the aims of the ruling class. As with language, the more you study real history--drop the textbooks and read the actual original documents and scholarly work on them--the more you understand that we have made all the same mistakes as any other country. But most people won't do that, and thus, most people are too easily manipulated, which equals millions of votes cast by the ignorant.
Orwell was more prophetic than you think.