“Nobody has any common sense these days!”
Common sense is the ability of commoners to "sense" what is true and what is untrue, without having to think about it. A related term is horse sense, the ability of an ordinary working-class citizen to intuitively understand that he is supposed to ride a horse instead of the other way around. Both terms are distinct from royal sense, which is the inability of kings and queens to stop bleeding when you cut them.
As a concept, common sense is similar to consensus, the philosophy that if many people believe something, they cannot possibly be wrong, unless those people are foreigners. It is, however, distinct from comsensus, which is a portmanteau of "common" and "sense" that does not exist in the English language.
Common sense reached its apex in America in the 1950s, when everyone had it. Unfortunately, no one these days has any common sense anymore. This is entirely due to the actions of hippies, lawyers, and Democrats.
Common sense in the pre-modern era
Common sense was rare in antiquity, and examples of its absence abound. For example, in 218 BCE, Hannibal marched an army of war elephants over the Alps in an attempt to conquer Rome, but managed only to significantly decrease the price of frozen elephant meat in Carthaginian markets. Another classic example took place about 250 years later, when a bunch of Jews started worshiping a dead carpenter.
An early attempt at defining the principles of common sense was undertaken by Thomas Paine in 1776, with his publication of the pamphlet "Common Sense." The pamphlet was an attempt to convince his countrymen to stop trying to fashion false teeth out of wood, as it tended to rot in their mouths, but it quickly devolved into a ludicrous anti-Monarchical tirade, forever relegating it to obscurity.
In 1922, Calvin Coolidge ran for President under the slogan "A return to normalcy." Some modern observers see this as an early attempt to lay down the foundations of common sense. Unfortunately, in 1922, "normalcy" referred to sub-prime lending and flappers.
On August 16, 1945, the day after VJ-Day, working-class Americans collectively realized that complex ideologies such as Communism, Fascism, and science had caused the death of millions of people, some of whom weren't even Jews. They reasoned that what the world needed was a new system of determining right from wrong. Thus, the guiding principle of common sense was arrived upon: If a bunch of folks say something in a thick drawl, it is true.
Common sense quickly gave rise to many important principles. The first of these principles was "look before you leap." That just seemed to make good common sense. Prior to 1945, an inordinate number of accidents had occurred due to people leaping into things without first looking to see what they were leaping into. In fact, the leading cause of death among senior citizens was "leapt into."
Common sense quickly solved this problem, and "leapt into" dropped seven places on the leading causes of death chart, to be replaced by "Mysterious lung illness of an unknown cause that is definitely not cigarette smoking." The common sense movement had been born.
Common sense in the 1950s
Throughout the 1950s, more and more common sense principles took root. "Don't piss into the wind" reduced the incidence of urine-stained trousers by nearly 80%. "America is the best country ever" reduced the incidence of living Koreans by 12%. And "Don't drink from the same fountain as colored people lest you catch Nigger Cooties" reduced the incidence of Nigger Cooties by 100%, although some liberals would later claim that Nigger Cooties was not a real thing to begin with.
This was the Golden Age of America, a period of time when everyone agreed on everything. The sole exception were the beatniks, who rejected the principle that all truth was spoken with a lazy drawl and instead asserted that all truth was spoken by alcoholics in black turtleneck sweaters. Fortunately, beatniks proved to be extremely stabbable.
The apex of common sense was reached on October 4, 1957, with the first broadcast of Leave It to Beaver. This television program depicted an American family with a great deal of common sense, including the sense to bestow a nickname on their youngest child that was a synonym for the vagina. The show related common sense principles to mainstream America such as "children should not cut their own hair" and "black people do not exist."
The death of common sense
Sadly, the era of common sense was not to last. In the early 1960s, teenagers began rejecting the common sense values of their parents because they were ungrateful little snots unwilling to act like men and get shot to death in Vietnam like they were supposed to. Instead, they began dying their clothes and aggressively neglecting their hygiene.
This set into a motion a chain of events that slowly unraveled all of America's common sense traditions. Before long, the incidence of urine-stained trousers began to rise, and finally, during the great Nigger Rights Outbreak of 1964, Americans everywhere realized that no one had any goddamn common sense anymore.
The worst, however, had yet to come. These children grew up to be lawyers and instituted bizarre and inscrutable layers of bureaucratic policies. For example, they assigned zip codes to American neighborhoods, causing their bewildered parents to remark that soon they'd be giving their children numbers for names. Soon, American society was hopelessly ensnared in confusing red tape. This phenomenon would later become the subject of the great literary work, "How Many Bureaucrats Does it Take to Change a Light Bulb?"
Postmodern instances of common sense
In the early 21st century, there has been a movement to resurrect common sense. This movement has been led by Alaskan ex-governor and failed vice presidential candidate Sarah Palin, who has repeatedly called for "commonsense conservatism" in American government.
Commonsense conservatism is the theory that any sentence preceded by the word "golly," and/or any assertion that annoys Alec Baldwin, is probably true. "Ask not what you can do for your country; ask what your country can do for you" is not a commonsense conservative concept, because it contains too many words, as well as a semicolon. However, "Golly, Alec Baldwin sure is gay," is.
Commonsense conservatism asserts that certain political policies should be undertaken because they have catchy slogans. For example, it posits that we should drill in the Arctic National Wildlife Refuge because "Drill, baby, drill." When a commonsense conservative is told that this is a non-sequitur, they are expected to reply, "Golly!"
Proponents of commonsense conservatism believe that the cause of commonsense conservatism is bolstered by repeating the phrase "commonsense conservatism" as often as possible. One who believes in commonsense conservatism is doing commonsense conservatism no favors by not continuously labeling all their political beliefs as "commonsense conservatism." When asked about commonsense conservative policies by a respected journalist such as Rush Limbaugh, a commonsense conservative will go to great lengths to remind that journalist that she is a commonsense conservative and that her policies are examples of commonsense conservatism.
Beyond the political sphere, a movement also exists among teenage nerds to resurrect the concept of common sense using image macros. The underlying philosophy of this movement is that if a nerd is able to identify that something silly is happening in a photograph, that nerd is by implication much smarter than the subjects of said photo.
Common sense image macros often take the form of "demotivational posters" with the caption "Common sense." In theory, this is a throwback to the original principle of common sense as a form of consensus, inasmuch as the creators are all doing exactly the same thing as one another (i.e., they believe it is common sense to create an image macro based on common sense, because everyone is doing it). In practice, however, it is a reflection of the fact that teenage nerds are not very creative.
In the example on the right, an X-ray of a mangled hand is depicted, with the caption "Common sense: get some!" This is because no one with any common sense could possibly become injured. It is intended to convey the message that the creator is superior to the subject of the photo, in that the creator has the ability to open a ketchup bottle.
A third example of common sense in the postmodern era is my mother, who is the only person in the world who has a lick of common sense anymore. This is, of course, according to my mother.