Saturday, September 13, 2008

Faulty Reasoning: False Causation (Cum Hoc Ergo Propter Hoc)

One of the oldest known fallacies is the argument that, if two things occur together, then one causes the other. That is, the fallacy of reasoning that the correlation of two things proves that there is a cause-effect relationship between them.

(True to its age, this fallacy has a Latin name: "cum hoc ergo propter hoc." It translates as, "with this, therefore because of this." Sometimes it is referred to as "post hoc ergo propter hoc"; "after this, therefore because of this.")

If two things (or sorts of things) -- call them "A" and "B" -- occur together (for instance, one occurs before the other), it certainly does raise the possibility that they have some causal relationship, such as that A causes B.

However, correlation does not entail (or imply, guarantee, or necessitate) causation. We shouldn't immediately conclude that A causes B, or that B causes A, just because A and B occur together. It could be that A and B are both effects of something else. Or it could be that A and B have no causal relationship whatsoever, and that their correlation is simply coincidence.

(To put it in logical terms, correlation is a necessary -- but not sufficient -- condition for a causal relationship.)

Illustrative Examples

Some examples should help illustrate the point:

  • If you're standing at the train station, waiting for a train to arrive, likely what will happen is that you'll first hear an announcement that the train is coming, and then the train will show up. But it would be silly to conclude that the announcement causes the train to show up. It's not as if making a new announcement will magically bring a new train into the station.
  • People who have a fever are often sick. They may faint, become ill, vomit, etc. But it would be a mistake to conclude that the fever causes the illness or vomiting. Often the fever (along with the fainting and vomiting) is itself the effect of the flu or an infection, which is the true cause.
  • Birds migrate away from the poles and toward the equator just before winter, but the migration of birds doesn't cause winter to happen.
  • It's often noted that there is a correlation between substance abuse and depression. But, does substance abuse cause depression, or does depression cause substance abuse? Or are the two just the effects of some other cause?
  • The students at a prestigious school have very high grades. Is that because the school does a good job at teaching them, or because the brightest students have all sought to be accepted into the school because of its reputation?
  • The people who go to a gym are all very healthy. Is that because the gym is doing a good job of getting them to exercise, or because health-conscious people tend to sign up for a gym?
  • Does watching pornography cause an obsession with sex, or is it the effect of such an obsession?
  • Does watching violent movies create a violent disposition, or do people who already have a violent disposition tend to watch violent movies?

Common Mistakes in Political Discussions

This form of fallacious reasoning -- "correlation implies causation" -- often comes up in the political arena in the context of monetary donations. That is, you often hear someone assert or argue, "Senator X supports such-and-such a position because he got money from a lobbyist or special interest group that supports the same position!" In other words, from the fact that the senator received money from a group supporting a particular position and the fact that the senator also supports that position, it is concluded that the money caused the senator's position. But this is fallacious. After all, it could be that the cause and effect are the other way around. That is, it could be that the group gave the senator the money because of his support for their position.

Another instance of this kind of fallacious reasoning is how we instantly link economic circumstances to the president or whichever political party is in power. That is, when the economy is good, we give credit to the president, implicitly arguing, "the economy is good while this person is president, therefore this president is the cause of the good economy." And we do the same when the economy is bad. We blame the president for bad economic circumstances, implicitly arguing, "the economy is bad while this person is president, therefore the economy is bad because this person is president." This is not to say that presidents or political parties play no role in the health of the economy. But making a connection between the two requires more than just pointing to a correlation. Because, after all, correlation does not imply causation.


Understanding causal relationships is very important to understanding moral issues. However, causality is a complicated empirical matter, and cause and effect relationships are not always obvious. We should be careful to avoid hastily concluding that one thing is the cause of another merely on the basis that the two things go together, or that one precedes the other.

"Now we have to overcome some big challenges, I will admit that. First, too many of our representatives in Washington are in the grips of a failed economic theory called trickle down economics. Now, I do not doubt their sincerity. But it has been proven wrong again and again. But there still are people in Congress who insist on cutting taxes for the wealthy instead of investing in our future. They careen from one self- inflicted crisis to another. Shutting down the government, threatening to default on our national debt, refusing to make the common-sense investments that used to have broad bipartisan support, like rebuilding our roads and our bridges, our tunnels, our highways, our airports. Or investing in better education from zero through high school and college. … And if the evidence were there to support this ideology, I would have to acknowledge that. But we have seen the results. Twice now in the past 30 years, a Republican president has caused an economic mess and a Democratic president has had to come in and clean it up."
-- Democratic presidential candidate former Secretary of State Hillary Clinton, June 22, 2016.

Comment: There are lots of things going on here. Where has it been proven that so-called "trickle-down economics" is a failed policy? Where has this policy been tested rigorously – that is, against an otherwise-identical control group? Such experiments are difficult to craft, and almost never occur on a large scale. It may be true that there have been cases where trickle-down economics has been implemented and bad economic news has followed, but it's propter hoc reasoning to jump to the conclusion that the former caused the latter. Correlation isn't necessarily causation. (Perhaps the bad economic news would have been even worse without the trickle-down policies, it's impossible to know unless you set up a control group for comparison.) Also, who has proposed not investing in our future? Perhaps people have proposed tax cuts for the wealthy along with spending less on investment than Clinton supports, but is there anyone who has said we shouldn't spend any money on education or infrastructure? This sounds like a straw man she's setting up to knock over. Finally, Clinton also resorts to "common sense" rhetoric, as well as "bipartisan" rhetoric (if the Republicans aren't supporting common-sense investments, then how can they have bipartisan support?).

"By almost every economic measure, America is better off than when I came here at the beginning of my presidency."
-- President Barack Obama, June 1, 2016.

Comment: The question, however, is whether the economy got better because of Obama’s presidency, rather than just during his presidency. We can’t simply conclude the former from the latter, that would be propter hoc reasoning. And, of course, there’s no control group economy (i.e., an economy without Obama as president) that we can compare the current one to in order to prove what difference Obama’s presidency made.

"America’s workforce is growing at the fastest pace since the year 2000. It is showing the kind of strength and durability that makes America’s economy right now the envy of the world despite the enormous headwinds that it’s receiving because of weaknesses in other parts of the world. In other words, the numbers, the facts don’t lie. And I think it’s useful, given that there seems to be an alternative reality out there from some of the political folks that America is down in the dumps. It’s not. America is pretty darn great right now, and making strides right now. … And I don’t expect that these facts and this evidence will convince some of the politicians out there to change their doomsday rhetoric, talking about how terrible America is. … The fact of the matter is, is that the plans that we have put in place to grow the economy have worked. They would work even faster if we did not have the kind of obstruction that we’ve seen in this town to prevent additional policies that would make a difference. … That’s what we should be debating. That’s the debate that is worthy of the American people. Not fantasy. Not name-calling. Not trying to talk down the American economy, but looking at the facts, understanding that we’ve made extraordinary progress in job growth; how can we continue to advance that, how can we make sure that people are successful in climbing the ladder of wage and income growth over the coming years; how do we make sure that we make this economy grow even faster. … The notion that we would reverse the very policies that helped dig us out of a recession, reinstitute those that got us into a hole -- plans that are being currently proposed by Republicans in Congress and by some of the candidates for President -- that’s not the conversation we should be having."
-- President Barack Obama, March 4, 2016.

Comment: There are several things going on here. First, Obama is accusing opponents (in particular, Republicans) of being "out of touch with reality", or perhaps of not caring about facts. Second, it sounds like he's also accusing Republicans of rooting for failure on the economy. Third, he is accusing them of obstruction. Fourth, he is calling for a higher standard of debate. Finally, he is making claims about what caused the Financial Crisis – he says it was Republican policies – and the reversal of that crisis – he says it was his own economic policies. But his support for these claims seems to be flimsy post hoc ergo propter hoc reasoning.

"Now, when you focus just narrowly on economic inequality, I've also been in that fight. I was in that fight during my husband's administration. And let's remember what happened there. At the end of eight years, we not only had 23 million new jobs, what was most important is incomes grew for everybody, not just those at the top, more people were lifted out of poverty, incomes rose, in the middle and working people. And today in Knoxville, in my town hall, I called on a man. He said, we never had it so good except when your husband was president. Because we tackled income equality and produced results, not talk, action. And that's what I will do as president."
-- Democratic presidential contender former Secretary of State Hillary Clinton, January 25, 2016, during the Democratic Presidential Candidates Town Hall Meeting, hosted by Chris Cuomo of CNN. Her remarks referred to the administration of her husband, former President Bill Clinton.

Comment: This is false causation (aka, "cum hoc ergo propter hoc") reasoning. Just because the economy was good while Bill Clinton was president doesn't mean it was good because Bill Clinton was president. Correlation is not causation. Besides, presidents don't influence the economy on their own, they collaborate on economic policy with Congress, and, for much of Bill Clinton's presidency, he faced a Republican Congress that opposed much of what he wanted to do. (Moreover, some might question whether the economy was truly good while Bill Clinton was president.)

"Overall, though, we’re making enormous progress, and it does make you wonder, why is it that Republican politicians are so down on America. Have you noticed that? I mean, they are gloomy. They’re like Grumpy Cat. Everything is terrible according to them. We’re doomed. I mean, I know it’s political season, but you listen to them and they’ve constructed this entire separate reality. It’s like the Twilight Zone. And according to their story, their narrative, everything was terrific back in 2008 when unemployment was skyrocketing and uninsured rates were rising and folks were losing their homes and their jobs, we were engaged in two wars, bin Laden was still at large. If you were listening to them, those were like the good old days. The golden years. And then I came in and the Democrats came in, but according to them that’s when everything all went to heck. Which is strange. I mean, it’s a hard argument to make. There was an article, I think, in The New York Times today, or maybe it was yesterday, where they pointed out that it’s very hard for them to make the arguments they make about tax cuts for the wealthy and doing the same stuff that they’ve been promoting, and trying to eliminate regulations on the big banks and all that, when the empirical evidence shows that when Democrats control the White House and we’ve got a Democratic Congress the economy does better and when they’re in charge, it does worse. Just look at the facts. Don’t take my word for it, go back, take a look at – all right, here’s Bill Clinton’s presidency, and then there’s Bush presidency and then there’s my presidency and, take a look. And you’ve gotta feel bad for the fact-checkers, for the Republicans, because they’ve gotta spend hours trying to keep up with some of the crazy stuff that their candidates are claiming. And the reason they have to make up stuff is because they don’t have a record to run on. They’re offering the same policies that caused so many problems in the first place. They ran on them in 2008, they ran on them in 2012, they’re running on them now. … And it's a shame when politicians spend all their time trying to make people feel bad, or more typically, trying to make them feel scared. Talking down the country all the time because it serves your politics. … We [Democrats] have got an optimistic vision about where this country can go if the politics of obstruction and fear-mongering are set aside and we start working together as a country."
-- President Barack Obama, October 23, 2015.

Comment: First, Obama seems to be accusing Republicans of rooting for failure, obstruction, divisiveness and fear-mongering, and saying they are doing so for "political" motives. This is unfair. Obama, when he ran for office in 2004 and 2008, was frequently critical of the country's state of affairs; does this mean he was "down on America"? Second, Obama is distorting Republicans' position: what Republican has ever said that everything was terrific back in 2008? Third, Obama is making a "correlation is causation" argument when it comes to the economy and Democrats, which is additionally flawed because Democrats and Republicans aren't monolithic when it comes to policies (some Republicans have raised taxes, like Ronald Reagan, and some Democrats have lowered them, like JFK), and because Republicans were in control of Congress during the boom years of Clinton's presidency, Democrats were in control of Congress when the Great Recession happened, and Congress is in control of Republicans now that we're making "enormous progress". Of course, sometimes good or bad things happen when a party is in power that were set in motion earlier by a different party, or that are out of anyone's political control altogether.

"And they talk the talk, but they don’t walk the walk. Their menu doesn’t have a whole lot of options for the middle class. The one thing that the bus full of people who are fighting to lead the Republican ticket all share is they keep on coming up with the same old trickle-down, “you’re on your own” economics that helped bring about the crisis back in 2007-2008 in the first place."
-- President Barack Obama, July 2, 2015.

Comment: This is "failed policies" rhetoric. What evidence does Obama have – apart from flawed post hoc ergo propter hoc reasoning – that Republican fiscal policy caused the Financial Crisis? Were Democrats – or, was Obama – offering any policies in the 2000 or 2004 presidential elections that would have prevented the recession?

"And I want to make this point, even though it’s a little off topic, but it oftentimes is the backdrop against which these debates take place -- if you listen to some of my political critics, they always want to paint me or the Democratic Party as this “tax and spend” and irresponsible. Let me say this -- since I came into office, the federal deficit has come down by two-thirds. It hasn’t gone up. It’s come down by two-thirds. So when Bill Clinton was President -- budget got balanced and we had low deficits. Then somebody else came in and -- deficits started going up. And then I came in and I inherited this huge recession that drove up the deficits. And then we started whittling them down -- even as we were expanding the earned income tax credit, even as we were expanding Pell grants -- because part of what we did was we said, well, let’s make sure the tax code is fair. Let’s make sure that we're eliminating programs that don't work to help middle-class families."
-- President Barack Obama, April 15, 2015.

Comment: This is false causation reasoning (post hoc ergo propter hoc). It's not the case that deficits (or economic conditions more generally) are the result of who is president at the time. A lot of other factors are involved. At the very least, Congress plays a role in determining the budget, and therefore how much money the government borrows (i.e., the deficit). Republicans had a majority in Congress much of the time when Bill Clinton was president, and Democrats had a majority in Congress when the "huge recession" struck (Obama himself, as a senator, was part of Congress). Should we therefore chalk the balanced budget up to a GOP Congress, and the recession to a Democratic one? No, that would be to reason just as flimsily as Obama does in the quote above. Obama also advocates for fairness, here.

[I]n the November 2014 exit polls, only 22 percent of Americans said they thought life would be better for future generations, and in Gallup’s latest “Economic Confidence Index” poll, 50 percent of Americans say the economy is getting worse. Not to mention, only 29.3 percent of Americans think the country is headed in the right direction, while 61.3 percent of Americans believe we are on the wrong track. … That bleak outlook is consistent with an essay Gallup chief executive Jim Clifton wrote at the beginning of this year, where he noted that, “Until 2008, start-ups outpaced business failures by about 100,000 a year. But in the past six years, that number has suddenly turned upside down.” Despite quoting this stunning fact, Edsall doesn’t make the connection between this negative economic data and a certain election in November 2008. Oddly, Edsall’s piece doesn’t even mention President Obama, except to identify a quote from the former chairman of Obama’s Council of Economic Advisers. Obama’s negative impact on the economy should be a lesson for the next president. I don’t think there has been a president in my lifetime who has been more hostile to business than Obama. … Anyway, all is lost for the remaining 21 months under Obama, and no doubt more businesses are doomed as a result of this administration’s anti-business bias.
-- Pundit Ed Rogers, April 6, 2015.

Comment: First, to simply blame Obama for the bad economic confidence numbers seems like post hoc ergo propter hoc reasoning. The financial crisis also happened during the latter half of 2008, couldn't that be a cause for the lack of confidence? Second, Rogers is demonizing Obama by saying he is anti-business. Even if it's true that Obama doesn't have the best policies for business (or better policies than his opponents), does that mean he actively opposes business?

"America, Rebekah and Ben’s story is our story. … You are the reason that I ran for this office. You are the people I was thinking of six years ago today, in the darkest months of the crisis, when I stood on the steps of this Capitol and promised we would rebuild our economy on a new foundation. … And over the past five years, our businesses have created more than 11 million new jobs. We believed we could reduce our dependence on foreign oil and protect our planet. And today, America is number one in oil and gas. America is number one in wind power. … And thanks to lower gas prices and higher fuel standards, the typical family this year should save about $750 at the pump. We believed we could prepare our kids for a more competitive world. And today, our younger students have earned the highest math and reading scores on record. Our high school graduation rate has hit an all-time high. More Americans finish college than ever before. … At every step, we were told our goals were misguided or too ambitious; that we would crush jobs and explode deficits. Instead, we’ve seen the fastest economic growth in over a decade, our deficits cut by two-thirds, a stock market that has doubled, and health care inflation at its lowest rate in 50 years. This is good news, people. So the verdict is clear. Middle-class economics works. Expanding opportunity works. And these policies will continue to work as long as politics don’t get in the way."
-- President Barack Obama, January 20, 2015, during the 2015 State of the Union address.

Comment: What evidence does Obama have that these accomplishments are the results of his policies, rather than the results of policies another president (or Congress) pushed for, or the result of forces outside the influence of the government? This seems like "cum hoc ergo propter hoc" reasoning — "it happened after I came into office, therefore it happened because I came into office" — which is flawed reasoning.


Examples from 2012.

"In 1981 our critics charged that letting you keep more of your earnings would trigger an inflationary explosion, send interest rates soaring, and destroy our economy. Well, we cut your tax rates anyway by nearly 25 percent. And what that helped trigger was falling inflation, falling interest rates, and the strongest economic expansion in 30 years."
-- President Ronald Reagan, May 28, 1985.

Comment: Reagan is using "failed policies" rhetoric on his critics, noting that they made false predictions about what his policies would do. But is Reagan resorting to false causation reasoning? Was the drop in inflation and interest rates, etc., caused by Reagan's policies, or just preceded by them?

(The list above is not intended to be a comprehensive record of all relevant examples.)

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