We can classify an argument as either "valid" or "invalid". There's really nothing in between the two categories. It's either "this or that". However, when we figure out it's an invalid argument, we can classify it even further by determining how strong or weak the argument is.
The easiest way to determine the validity of an argument is to check the possibilities. If it's impossible for the premises to be true and the conclusion to be false at the same time, it's a valid argument.
For example:
A "good" baseball team has a win/loss record over .500.
The San Francisco Giants have a win/loss record of .558.
The San Francisco Giants are a good baseball team.
This is a valid argument because there's no possible way the conclusion can be false when both premises are true.
When determining how strong an argument is, the main thing to look at is how specific the premises are. A "weak" argument has a good possibility of the premises being true and the conclusion being false. A "strong" argument has some possibility, but it's extremely unlikely.
For example:
Animal allergies can cause watery eyes and nasal congestion.
Mary has experienced these symptoms around dogs.
Mary is only allergic to dogs.
There are several possibilities for the premises to be true and the conclusion to be false. The time Mary has experienced these symptoms around dogs, there could have been cats around also. Nothing in the first premise is specific to dog allergies either, those symptoms are caused by any allergy. Mary could be allergic to grass or many other features of parks, which could be the only place Mary ever runs into dogs. There are too many possibilities for the conclusion to be false and the premises be true. This is a weak argument.
A stronger version of that argument would be:
Mary experiences watery eyes/sneezing when at a friends house who owns a dog.
Mary otherwise doesn't have allergic reactions at her other friends houses, including her own.
Mary is allergic to dogs.
This is a stronger argument as it's more specific. The more specific an argument is, the more the possibilities you rule out of the premises being true and the conclusion being false. There's still the possibility that Mary is allergic to maybe a certain perfume or certain carpet shampoos her dog-owner friend owns, but it's unlikely.
Hey man I really like this post on strong and valid arguments. Not only is it very informing, your examples are interesting topics which makes it easier to understand the concepts. The valid argument about the San Francisco Giants works because any team over with over a .500 win percentage is definately a good team, and makes for a valid argument. Not only that, but I am definately pulling for them to make the playoffs this year because they are having a great season, and have a good to chance to go to the World Series if their pitching staff keeps it going. Also, using an allergy example is a good way to go when talking about strong arguments. I used an allergy example also because I work in a restaurant and hear customers making arguments all the time about some allergy they have.
ReplyDeleteI really found this post interesting because you use really good examples. Your examples were that good that it made it easy to understand the difference between strong and valid arguments. I had a hard time understanding the difference between strong and valid arguments because they seem so much a like or at least to me. I really like the example you use as a valid argument about the San Francisco Giants. You made it simple to understand a valid argument that in order to be true the premises has to be true as well as conclusion. For instance your example of that a good baseball team has to be over .500 and the Giants are over .500 team therefore a good baseball team.
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