4. Conclusions presented by a source are arguments. Arguments must meet certain criteria to be worth consideration; otherwise they are thrown out out-of-hand, unless it can be reformulated as a correctly-structured argument.
Conclusions are not taken from external sources, but arguments can be accepted for consideration. Arguments are conclusions along with their supporting data; the conclusion contained is used only as a metric to which you will compare your own conclusion.
It may seem that critical thinking is a lot of work because of the intensive validation that is required for all incoming data. This is true, but it is counterbalanced by some additional tools of thought that critical thinking will place into your mental toolbox. We've already mentioned a few of these, such as considering the source of the data, or flagging data as tentative. But by far the most powerful is the ability to reject many arguments out-of-hand for being improperly formed.
By learning to recognize common fallacious argument constructions, you can skip the data validation step or in fact any further consideration. Unless the argument can be re-formed to adhere to the proper requirements, it is of no value.
Let's take a look at a few example arguments.
"Bruce wants to reduce funding to our police department. I guess he'd like to see crime running rampant in our town."
"A lot of the people supporting the proposed legislation to loosen gun control have criminal records. Obviously they just want to be able to get guns so they can commit more crime."
"I know that cigarettes are bad for you because my teacher told me so."
"We can't change our policy for employee lunch breaks. This is just the way it's always been."
"The Definitive Guide to Car Repair says that Joe is one of the best mechanics in the world. In fact, Joe wrote that book, so he must really know his stuff!"
"If I let you stay out late, then pretty soon everyone will want to!"
"I washed my car this morning, and then it rained this afternoon. My carwash must have caused the rain."
All of these are argument and include supporting data which may be itself correct. But they are all spurious and should be rejected or reformed before you consider them. Let's look at the name for each type of fallacious argument and why each type is never valid.
"Bruce wants to reduce funding to our police department. I guess he'd like to see crime running rampant in our town."
This one is the Straw man. The straw man is so common an approach to argument that one scarcely goes a day without encountering it. Here, the presenter gives a distorted impression of the reasoning or motives of their opposition. Bruce may have any number of reasons for wanting to reduce police funding, but it's unlikely that he (or anyone else) wants to see crime running rampant. But by giving a distorted version of the opposing position, the presenter can then set about destroying it with ease.
"A lot of the people supporting the proposed legislation to loosen gun control have criminal records. Obviously they just want to be able to get guns so they can commit more crime."
Ad homineum arguments attack those who hold the opposite position, rather than the position itself. The supporters of a position are irrelevant to the truth or falsehood of its data, or the value of its conclusions. Imagine you were told that many clinically insane people believe that the Earth is round. Would this sway you to think that the Earth is not round? A popular ad homineum argument is "Hilter was a Christian," with the implied conclusion being the the teachings of Christianity are untrue or unworthy. You can find respected and despised examples of people that hold almost any position. That has nothing to do with the merit of the position itself.
"I know that cigarettes are bad for you because my teacher told me so."
The Appeal to authority taps into our natural trust of authority. As we have already covered, trusted sources (like your teacher) may be given more consideration than untrusted ones. But just because someone is trusted or in a position of authority does not mean that you should take everything they say at face value. The appeal to authority was used by slaveholders during the 19th century. They claimed that because slavery was already a part of American law, it was therefore morally acceptable. Of course the law and the government can be wrong - even spectacularly so, as in this case. A lighter example might be your mother telling you to eat your broccoli because "I'm your mother and I say so." Next time she says that, you can respond with "Mom, that's an appeal to authority argument, which is spurious. Please restate your argument with supporting data, such as the health benefits of broccoli."
"We can't change our policy for employee lunch breaks. This is just the way it's always been."
The Appeal to status quo has a sadly defeatest feel to it. Something being one way or another in the past has no bearing on whether it was a good idea, either then or now. We can't do anything about the past, but we can and should do something about the present and the future.
"The Definitive Guide to Car Repair says that Joe is one of the best mechanics in the world. In fact, Joe wrote that book, so he must really know his stuff!"
Circular reasoning, also known as begging the question, appears frequently in legal and religious debates (such as the slaveholder example, above). In this case, the premise for Joe's world-class knowledge of car repair is that it is stated in a book. While books can be valuable resources for information, it only makes sense to accept this if the evaluation of his abilities was made by some other author or mechanic. It's called circular reasoning because you can go around in a circle infinitely trying to get the root piece of data.
"If I let you stay out late, then pretty soon everyone will want to!"
This is the Slippery slope argument. There is such a thing as a slippery slope, but in and of itself it is not a good argument. Just because you let one of your children stay out late on a special occasion doesn't necessarily mean that your other children will want to do the same, or that you will then be obligated to let them. A more tenble restatement might be "If I let you stay out late, I feel it would be unfair to your older siblings who have never gotten a curfew exception."
"Ever time I wash my car, it rains the next day. My carwash must cause the rain."
Remember causality? Post hoc is the common reasoning mistake that just because something comes after something else, it was caused by it. This is a correlation, not causation. (In this case, it probably isn't even correlation, but just a case of remembering the times that the two event matched up and forgetting the times they didn't.)
These are just a few common fallacious argument types. You can find many more by doing a websearch. This page has a fairly complete list:
http://www.opifex.cnchost.com/reasoning/fallacies/index.htm
Once you've identified a fallacious argument, what next? Well, if possible, you may want to alert the source that you need a better argument. In most cases - say, something you saw on TV - this will not work. Instead you can try to restate their argument yourself, which will allow you to move onto the next stage of verification. Returning to this example:
"We can't change our policy for employee lunch breaks. This is the way it's always been."
...you might speculate that what they are really saying is that changing the policy would require an investment of time and energy by the Human Resources department of the company, and they are currently very busy with more important things. This is a better argument: the company cannot devote resources to your request (changing some policies) because it has already allocated them to more important tasks (perhaps handling the hiring of new employees to help take the pressure off an overworked staff). The conclusion contained within suggests a better course of action for getting what you want: mention to the HR personnel that you'd like to get the policy changed, but understand they are busy with more important things right now. Return in a few months when they are less busy and bring the matter up again.
Another one:
"I know that cigarettes are bad for you because my teacher told me so."
The obvious immediate question here is "Why did she say they are bad?" You may get an answer like "she says they cause lung cancer," which would allow you to restate the argument as: cigarettes are bad for your health because they cause lung cancer. With a valid argument in hand, you can proceed with the next step: verifying whether or not medical science has proven that they cause cancer.
One more:
"Bruce wants to reduce funding to our police department. I guess he'd like to see crime running rampant in our town."
Straw men are easy to get around: go find out what Bruce has to say. Chances are, he will give a more plausible reason like "we need the money for our schools" or "crime is not a problem in our town, our police officers don't even have enough to keep them occupied" or "state funding has increased, so reducing our town's funding just keeps them at the same budget." Additionally you should look for other points of view: straw men can also lead you into thinking that there are just two possible perspectives, a false duality. A general search for information on the police department's current funding and activities, the level of crime in the town, and the larger picture of the town budget (I.e., where will the money go if not to the police?) may be very illuminating.