Debating Tips

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Having trouble recognizing and refuting bunk claims?

Big Ideas: 
  • Evidence supporting one side of an argument doesn't refute evidence for the other side
  • Correlation does not imply causation
  • The validity of a study can be challenged
  • You don't have to trust other people's interpretations
  • Nobody's right all the time

Evidence supporting one side does not refute evidence for the other side:

Suppose someone finds that Pluto is warming up, which, in their mind, lends credibility to the idea that global warming on Earth is caused by the Sun heating up1. Suppose that other studies confirm this. This person then contends that the Intergovernmental Panel on Climate Change (IPCC) report stating that sun-induced global warming is negligible compared to anthropogenic (human-caused) global warming is incorrect. This is bad logic: this person is using the fact that his/her data are correct to boost the validity of his/her conclusion over the IPCC conclusion. Simply because a study's data are correct does not mean its conclusion must be as well. For example, there is no reason why Pluto and Earth have to be warming for the same reason but it should be investigated further.

Correlation does NOT necessarily entail causation:

Let's talk a bit about correlation, which is a fancy term meaning a relationship between two quantities (such as mass, volume, energy, number of puppies, etc). Correlation can be positive (increase in one quantity means an increase in another), negative (increase in one means a decrease in another), or nonexistent. Correlation may indicate causation, or it may not. A graph showing a positive correlation between driving speed and crashes may be interpreted, rightly, as meaning driving at high speeds results in more crashes. It can also suggest, nonsensically, that crashes cause high-speed driving. You have no way of knowing just from the graph, and you need more information to figure out causation. A third possibility is that both quantities are affected by a third, un-graphed quantity. Suppose you do a graph, which shows a "correlation" between long marriage and receding hairline. It's nonsense to suggest that receding hairlines cause long marriages, or (I suppose) long marriages cause receding hairlines. But both could be due to age. A fourth possibility is that the correlation is by accident. Someone once did a wonderful correlation on solar power and stock market prices. . .

 The validity of a study can be challenged:

A source's reputation can be doubted. Check the funding of studies. Find out what organizations certain scientists are involved in. Remember, however, that just because a scientist is affiliated with the American Association of Petroleum Geologists or the Sierra Club does not mean he or she cannot do a good study. Once you become suspicious, challenge a paper's methods of data collection and analysis, or, if the methods are very complex, look for other papers that do so (they often do exist).

 You don't have to trust other people's interpretations:

If your "opponent" has given you a set of studies, read them yourself when you get the time. If you find fault with your opponent's analysis, mention it to him or her, and be prepared to state what fault you found. We encourage you to read our document with a grain of salt; if you find something strange, go look at our sources and/or email us!

 Nobody's right all the time:

If you can't challenge an argument you're presented with, you might consider re-evaluating your own position. You might not expect it, but what it often takes to convince a contrarian is to concede when they've made a good point.

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