Language, Truth, and Grammar
It would be convenient if only true statements were grammatical. Then we would be able to read truth-value off grammar. Falsehood would be signaled by ungrammaticality. But of course false statements are as grammatical as true ones. Grammar is completely indifferent to truth. The world is what determines truth not grammar. Meaning is not indifferent to truth, since in combination with reality it determines truth; and some truths depend on meaning alone. But the grammatical form of a statement tells us nothing about its truth even in conjunction with reality; and “Bachelors are unhappy men” has the same grammatical form as “Bachelors are unmarried men”. Grammar is neutral as to truth: it will generate a falsehood just as readily as it will generate a truth. Perhaps we can say that grammatical sentences ought to be true—that is their point—but “ought” does not imply “is”. The rules of grammar are simply not designed to produce the truth, the whole truth, and nothing but the truth. The machine in our head that generates infinitely many sentences from a finite number of elements is a falsity-generating machine as much as a truth-generating machine. When a child learns how to speak grammatically he or she learns how to construct false sentences as well as true ones. Grammar can never keep a child on the straight and narrow truth-wise (hence all the lying). Grammar will happily lend itself to either enterprise.
There are two aspects to this looseness of connection between grammar and truth: truth of belief and truth of utterance. Utterances (chiefly assertions) can be false as well as true without detriment to grammar, so that error and deception in speech are grammatically possible. People can tell lies while using grammar correctly (but not when using it incorrectly so as to produce nonsense). And beliefs can be expressed in a language of thought with full grammatical correctness and not be true. Thus grammar can be viewed as a device that permits falsehood in communication and in thought; it is no impediment to either. Indeed, it sets them up for falsehood by making falsehood eminently feasible. It thus makes humans prone to error in a way that non-speaking creatures are not. Animals are capable of both deception and error, so falsehood is part of their mental universe, but they don’t have the facilitating aid of grammar to work with. An animal may be under a perceptual illusion and so form a false belief, and deception is analogous to the lying assertion; but animals are not confronted by the enormous array of possible falsehoods that we speakers are. Our mental universe is brimming with the possibility of falsehood just by virtue of possessing grammar: most of those infinitely many sentences are false, and we have equal mastery of the false ones. We can envisage falsehood all too easily: it is built into our linguistic brain mechanisms. And this means that we can be victims of falsehood all too easily: false sentences can form in our mind according to the rules of grammar, and speakers can transmit falsity by exploiting the mechanisms of grammar. Telling lies and believing falsehoods are things we can do with the greatest of ease, given that grammar has the power to do both. If you don’t have a grammar module in your head, your opportunities for falsehood are greatly reduced. It is much harder to lie if all you have to go on is your skin coloration, and error is limited by the possibilities of perceptual illusion. In humans false belief can be induced by means of the faculty of speech, and speech itself is extremely liable to error. Anyone can produce a false utterance at any time, intentionally or otherwise; and the language of thought can easily operate to generate a false sentence inwardly. Grammar is what makes all this possible: it is the mechanism whereby profligate falsehood enters human life. Not the only one, of course, since we are also capable of perceptual illusion and logical fallacy; but it is the mechanism that allows falsehood on a grand scale, because of its truth-indifferent combinatorial powers. It is the main engine of cognitive malfunction, i.e. false belief. Think of all those conspiracy theories: they are spread by means of language (not by actually seeing what they purport to report), and language works according to the combinatorial powers of grammar. Grammar cares nothing for their absurdity or harmfulness; it just dutifully goes about its constructive business. How did Iago induce so much falsehood in Othello’s credulous mind? Almost entirely by exploiting the power of grammar to construct a false narrative (that business with the handkerchief was strictly secondary). Iago was slyly adept at using grammar to construct linguistic strings that would act on Othello’s receptive mind so as to produce false beliefs. It would be far more difficult, if not impossible, to achieve the same deceptive ends without the power of grammar. Grammar is not at all falsehood-averse; it is not intrinsically oriented towards the true. 
This means that language is a two-edged sword: it enables great feats of truth production, arguably the basis of human civilization; but at the same time—and for the same reason—it permits vast quantities of falsehood production. So grammar is both a very good thing and a very bad thing. From a certain perspective, it can be viewed as a genetically determined disease—the cause of untold error, delusion, paranoia, propaganda, and madness. It fills our heads with garbage, frankly. It’s like a parasite that eats into our mental universe, constantly generating new forms of error—a kind of psychological virus. Once a person is infected with the grammar virus her mind goes berserk—or it easily can once the mechanism is in place. A person lacking a language faculty will be far less prone to error simply because he lacks the mental machinery that enables it; you will not get very far brainwashing such a person or haranguing him into accepting the latest nonsense. But this very source of epistemic pathology is also the foundation of language in all its beauty and fecundity—its ability to convey and express truth. So grammar is a gift with a distinctly double existence: the ability to create great things, but also the correlated ability to introduce virtually unlimited error into human thought and culture. Before humans evolved language they were mentally limited in obvious ways, but they were also free of the side effects of a language faculty like ours. It is the unlimited and unconstrained potential of grammar that makes it such a rich source of error in human life: it has extraordinary productive power combined with absolute indifference to truth. An utterance (or a belief) has exactly the same appearance whether it is true or false, precisely because grammar is truth-neutral, and this enables it to function as a source of false belief as well as true belief. If grammar were truth-sensitive, we could tell the true from the false just by establishing grammaticality, but that is precisely what we cannot do. Indeed, it is hard to see how it could be done given that the objective world and the grammatical faculty are distinct existences: how could the internal rules of sentence formation depend on what is going on in the external world? The grammatical faculty is a kind of formal computational system operating by its own rules, but what makes sentences true or false lies outside this system. So any language like ours will necessarily contain grammatical rules that allow the formation of false sentences, with all that that entails. Language is necessarily a falsehood generator as well as a truth vehicle. It is, in fact, the most prolific falsehood generator on planet earth. It made the human brain into a hotbed of error. Because of language we must constantly be on our guard against falsehood—we are haunted by its possibility. This is why we are always correcting each other’s false beliefs. But animals don’t live in this world of lurking falsehood: they don’t need to argue with each other all the time, criticizing, correcting, disputing. Animals mainly believe what is true without having to worry about believing the false, but humans are rightly concerned about the truth status of their belief systems, given the prevalence of falsehood. We are, in a way, the victims of our own good fortune as grammatical speakers (and thinkers). It is entirely possible that our propensity to error, aided and abetted by our talent for grammar, will lead to human extinction (global warming, nuclear weapons). Of course, grammar alone is not responsible for such disasters, but it is a dangerous force needing elaborate policing—anarchic in its powers of falsehood generation. It is too creative—too free, too untrammeled. Truth cannot hold it back. It is, as it were, intellectually unethical—a kind of truth psychopath. It is as capable of falsehood as it is of truth, and doesn’t much care which way it goes. It is value-neutral, yet it generates structures that have the normative properties of truth and falsehood. Grammar produces syntactic structures, but syntactic structures don’t care whether they are true or false; yet these structures shape the very architecture of the human mind. It is syntactic structure that permits propaganda, mental manipulation, and fallacious reasoning—as well as true belief, science, and logical thought.  When syntactic structures participate in the transmission of falsehood they act in ways that are potentially harmful, but they are as prepared to do that as to transmit truth. The syntactic machinery goes about its nimble carefree business in complete oblivion with regard to truth or falsehood. It is rather like the biological machinery of cell production, which can produce healthy tissue or unhealthy tissue. Like many biological adaptations, it is a mixed bag of the useful and the detrimental; it remains to be seen how damaging its propensity to allow error will be. There is some reason to believe that the human mind actively prefers error to accuracy, and grammar gives it ample scope to indulge that preference.
I can imagine a science fiction story in which an alien population is placidly going about its business without the benefit of a grammatical language, believing mainly the truth and not being susceptible to propaganda and other forms of nefarious persuasion. Then a clever scientist invents a device to be inserted into the brain that will produce things called “sentences”, which will join with existing cognitive structures to enhance thought and enable communication. The invention is greeted as a great advance, but the inventor has not reckoned with a side effect of the device: it keeps producing false sentences because the rules of sentence formation have no filtering mechanism to inhibit the production of such sentences. The result is that the population starts to experience an enormous increase of erroneous belief and misleading speech, some of it quite harmful. But the device is now firmly implanted and cannot be safely removed. The people degenerate into a nattering horde of delusional fools, incapable of distinguishing truth from falsity, believing any groundless nonsense that comes along (they have no cognitive immune system capable of excluding false beliefs). Soon there is war and famine and general strife, along with the rejection of all science—and we know where this will all end. Eventually the species dies out, victims of a technology they could not control. Death by Grammar, it might be called. If dinosaurs went extinct by being too big, where once this was an advantage, we ourselves might go extinct by being too grammatical—too prone to the falsehoods facilitated by the grammatical faculty. We will leave behind us all those creatures not endowed with a language faculty that is powerful enough to create error unlimited. We will have perished from our own language instinct. 
 Fiction uses grammar in exactly the same way factual discourse does; there is no grammatical marker for fictional language. Grammar is promiscuous as between fact and fiction, capable of functioning in both domains. And fiction is a very natural deployment of our grammatical faculty, ancient and spontaneous. We can even imagine a tribe speaking only fictional sentences. This tells us a lot about the connection between the language faculty and truth, i.e. the lack of connection. Grammar is really an abstract formal structure on which truth and falsity can equally be hung (vide Chomsky).
 Language and politics are closely connected: language is what politicians use to persuade and manipulate. Oratory is the main tool in the politician’s toolbox. They use syntax (inter alia) to encourage assent and obedience, often to falsehoods; politics might be defined as the artful promulgation of the false by means of syntax (along with semantics and pragmatics). It is not an accident that Chomsky is interested in both linguistics and politics, the latter being an application of the former. Generative grammar forms the underlying machinery of political discourse: it facilitates and promotes such discourse. No generative grammar, no politics as we know it: grammar is ideally designed to this end given that it is sublimely indifferent to truth. Political speech makes ample use of the power of grammar to generate falsehood.
 Bear in mind that spoken language hasn’t existed for long in human history, let alone in world history (about 200,000 years by most estimates). So the long-term effects of grammar on survival are not yet clear (ditto advanced intelligence): it might turn out to be maladaptive in the end. Clearly the fertile capacity to generate error is a serious design defect, which might ultimately prove calamitous (I’m thinking particularly of climate change). Are there species elsewhere in the universe made extinct by their powers of syntactic production? Mythology is an offshoot of grammar, and mythology is pure falsehood (the Homeric gods etc.). The same is true of religion and ideology. The possibility of error is the price we pay for our linguistic creativity, and the price may be greater than we realize.