Alcohol has long been recognized as a useful social lubricant for parties and gatherings. Yet few of us understand the historical importance of intoxication, and the fundamental role it has played in forming societies. In this article, Edward Slingerland argues that alcohol helps us to access truth, and posits that intoxication should be taken seriously as a tool for building consensus and harmony in an increasingly divided world.
A recently-discovered ancient Chinese text, dating to the 4th or 3rd century BCE and written on bamboo strips, contains the evocative declaration “harmony between states is brought about through the drinking of wine.”  In ancient China political agreement was reached without the participants first voluntarily impairing their brains with carefully-timed and calibrated shots of liquid neurotoxin. The Roman historian Tacitus noted that, among the barbarian tribes of Germany, every political or military decision had to be run through the gauntlet of drunken communal opinion:
It is at their feasts that they generally consult on the reconciliation of enemies, on the forming of matrimonial alliances, on the choice of chiefs, finally even on peace and war, for they think that at no time is the mind more open to simplicity of purpose or more warmed to noble aspirations. A race without either natural or acquired cunning, they disclose their hidden thoughts in the freedom of the festivity. Thus the sentiments of all having been discovered and laid bare, the discussion is renewed on the following day…They deliberate when they have no power to dissemble; they resolve when error is impossible. 
Although Tacitus patronizingly portrays this use of truth-serum use of alcohol as a primitive, barbarian practice, the ancient Romans and Greeks themselves relied heavily on precisely the functions. Indeed, the idea that drunkenness reveals the “true” self, though ancient and universal, is perhaps most famously expressed by the Latin in vino veritas, “in wine there is truth.” This perceived link between honesty and drunkenness goes back to the Greeks, for whom the combination of “wine and truth” was a truism. “Inappropriate sobriety was thought highly suspect,” the writer Iain Gately notes. “Some skills, such as oratory, could only be exercised when drunk. Sober people were coldhearted—they meditated before they spoke and were careful about what they said, and therefore…did not really care about their subject.” 
Since drunken words are spoken straight from the heart, they have historically been accorded greater weight than communications from the sneaky, controlled, and calculating self. In ancient Greece, oaths declared under the influence of wine were viewed as particularly sacred, reliable, and powerful. The Vikings similarly accorded an almost magical reverence to vows made after drinking (heavily) from a sacred “promise cup”; in Elizabethan and Stuart England, public declarations were viewed with suspicion unless they were accompanied by toasting with alcohol. 
Alcohol is the most commonly-used truth-telling technology, but it is revealing that in regions without alcohol other intoxicants play an identical role.
My favorite illustration of the truth- and trust-enhancing function of alcohol is fictional, from the TV show Game of Thrones. In the famous “Red Wedding” episode, two rival clans have apparently overcome their differences and agreed to unite against their common enemy. As humans are wont to do, this agreement to cooperate is celebrated and reinforced by an alcohol-soaked, wildly drunken banquet. In the midst of the revelry, a servant begins to pour more wine for Lord Bolton, a decidedly shifty character, but he puts his hand over the glass. When his drunken neighbor asks him, incredulously, why he isn’t drinking, Bolton replies tersely, “Dulls the senses.” “That’s the point!” is the cheerful reply. Indeed, that is the point. As any Game of Thrones fan is aware, Lord Bolton is a classic defector, keeping his mind clear so that he can direct the cold-hearted murder of all of his drunken “friends.” The take-home lesson is: keep your eye on the guy who isn’t keeping up with the toasts.
Alcohol is the most commonly-used truth-telling technology, but it is revealing that in regions without alcohol other intoxicants play an identical functional role. The earliest European explorers in the Pacific reported being welcomed and having their degree of threat assessed through kava-centred banquets.  To this day, no Fijian village counsel can begin deliberations until all present are appropriately high on kava. Similarly, among Woodlands and Plains tribes in North America, rival chiefs settled disputes and concluded conflicts over the calumet or “peace pipe” later celebrated in Hollywood Westerns. What was conspicuously left out of these cinematic recreations was the intensely intoxicating effect of these hallucinogen-laced smokes. “Custom dictated that if the calumet was offered and accepted, the act of smoking would make any engagements sacred and inviolable,” notes the historian of American religion Robert Fuller. “It was thought that anyone who violated this agreement could never escape just punishment.” 
Cultures throughout time and across the world implicitly understood that the sober, rational, calculating individual mind is a barrier to social trust.
The fact that, when alcohol is taken out of the equation, other chemical intoxicants are tapped to fill the same functional role is a strong bit of evidence against any hijack or hangover theory. Although they did not enjoy the benefits of modern neuroscience or social psychology, cultures throughout time and across the world implicitly understood that the sober, rational, calculating individual mind is a barrier to social trust. This is because human beings, especially those living in large-scale societies, constantly face cooperation dilemmas that can only be solved by abandoning rational self-interest, but that also leaves one vulnerable to being taken advantage of. We need to trust even though there is a constant temptation—in others as well as ourselves—to be selfish and reap benefits at the expense of the group.
This is why it is common for drunkenness—often serious drunkenness—to be obligatory for important social occasions, business negotiations and religious rituals. An ancient Chinese poem from the Book of Odes declares:
Sopping lies the dew;
Not till the sun comes will it dry.
Deep we quaff at our night-drinking;
Not till we are drunk shall we go home.
The Jewish holiday of Purim, honouring Mordecai’s victory over the genocidal Haman, similarly demands that the celebrant become so inebriated that he or she cannot tell the difference between “Cursed by Haman” and “Blessed be Mordecai.”
How do alcohol and other intoxicants perform this truth-revealing function? One thing that they all have in common is their ability to impair the functioning of the prefrontal cortex (PFC). The PFC is a very important part of the brain, the centre of what cognitive scientists refer to as executive function or cognitive control: our ability to repress emotions, delay gratification, stay focused on a task, and keep contradictory or complex things in our mind. It is also crucial to deception. Cheating or lying requires cognitive control. It’s easy and effortless to appear honest or sincere when you are telling the truth or expressing a genuine emotion; formulating a lie or faking an emotion requires effort and attention. If you want to make it harder for liars to lie, one promising approach would be to exploit this weakness by downregulating their cognitive control.
Just as we shake hands to show that we are not carrying a physical weapon, communal intoxication allows us to cognitively disarm in the presence of others.
There is therefore a very good reason why, in societies as different as those in ancient Greece, ancient China, medieval Europe, and the prehistoric Pacific Islands, no gathering of potentially-hostile individuals occurred without the inclusion of staggering quantities of intoxicants. The threat presented by the hypocrite, the false friend, is an existential one for any community. This is why helping to unmask fakers, and thereby solidify interpersonal trust, is a crucial function that intoxicants have played in human civilization. Just as we shake hands to show that we are not carrying a physical weapon, communal intoxication allows us to cognitively disarm in the presence of others. By the tenth toast of sorghum liquor at a Chinese banquet, or the final round of wine at a Greek symposium, or the end of Purim, the attendees have all effectively laid their PFCs on the table, exposing themselves as cognitively defenseless.
A line in Plato’s Symposium declares that “truth is revealed by wine and children”—a very telling equation of the sort of PFC impairment shared by children and drunks. Intoxication has therefore played a critical role in helping humans get past the cooperation dilemmas that pervade social life, especially in large-scale societies. For groups to move past suspicion and second-guessing, our sneaky conscious mind needs to be at least temporarily paralyzed, and a healthy dose of chemical intoxicant is the quickest, most effective, and most pleasant way to accomplish this goal.
This suggests that our recent neo-Puritanical zeal to banish alcohol from professional events, or shame those who pump more CO2 into the air flying to in-person conferences, is misguided. While we should rightly be worried about the dangers of mixing alcohol and semi-obligatory socializing and concerned about our carbon footprint, there is an ancient and distinctive mode of socializing that can only be achieved through the communal, in-person consumption of intoxicating substances. Understanding that wet office parties are not just about having fun, but also building trust and group bonding, allows us to make more intelligent decisions about when and if they are appropriate.
Debates about the proper role of intoxicants in our lives need to be informed by our best current scientific, anthropological and historical scholarship, which at the moment is far from reality. Getting the right perspective will put us in a place to more clearly see what concrete trade-offs we face when we formulate policies and make personal decisions about the role of intoxicants in our lives. Our desire for alcohol is not an evolutionary mistake. There are good reasons why we get drunk. No informed decision, at either the individual or social level, can be made without a better appreciation of the role that intoxication has played in creating, enhancing, and sustaining human sociality, and indeed civilization itself.
 This phrase appears in “King Cheng’s Trip to Chengpu” a, Chengyuan (Ed.). Shanghai Bowuguan Cang Zhanguo Chu Zhushu IX 上海博物館藏戰國楚竹書（九）. Shanghai: Shanghai Guji. 2012: 148).
 Quoted in Forsyth, Mark. A short history of drunkenness. New York: Viking.2017: 95.
 Gately, Iain. Drink: A cultural history of alcohol. New York: Gotham Books. 2008: 15
 McShane, Angela. (2014). Material Culture and ‘Political Drinking’ in Seventeenth-Century England. In Phil Withington & Angela McShane (Eds.), Cultures of Intoxication, Past and Present (Vol. 222, pp. 247-276): Oxford University Press. Also, Gately 2008: 12 on Greek oaths, Forsyth 2017: 126-127 on Viking oaths.
 Lebot, Vincent, Lindstrom, Lamont, & Merlin, Mark. Kava: The Pacific Drug. New Haven: Yale University Press.et al. 1992: 119.
 Fuller, Robert. Stairways to Heaven: Drugs in American Religious History, . Boulder: Westview Press. 2000: 37.