Critical Thinking, by Adam Wiggins
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A few basic terms must be defined before we can proceed:

Data - Basic, raw information which describes something that exists in the world. The most useful data is objective (like "the sky is blue") but it can also be subjective ("I felt happy when I looked up at the sky"). Arguments and conclusions (see below) are NOT data, even though people will often present them as such.

For example, a value judgment like "this jacket is great" or "that restaurant has the best spaghetti in town" are not data, but conclusions. Data in these situations would be something like "the jacket is red, has lots of deep pockets, and is very well-insulated" or "the restaurant serves spaghetti and other pastas, many of my friends have said that they like the food there, and the time I ate there I enjoyed it."

Premise - Data presented in support of an argument.

Argument - An assertion based on data. Arguments always take a certain structure, like so:

<conclusion> because <premise>.

or sometimes

<premise>, therefore <conclusion>.

An argument is simply a conclusion which is being presented to you, typically by an external source, but it can also be something you are considering internally. For example, if a friend says, "You'd love this jacket because it's your favorite color and it's got plenty of pockets," this is an argument. You may choose to accept their conclusion (that you would like the jacket) if you can verify their data (it's your favorite color, it's got plenty of pockets). Arguments typically include a large amount of implicit data, known as assumptions.

Assumption - Implicit data not included with the statement of an argument. This is a necessary part of human communication, but it is also one of the most problematic parts. Assumptions require both parties to have existing, accepted data; and for both parties to know the other party already has this data. Many times arguments can sneak data into your mind by disguising it as an assumption. Like a spy slipping into the colony using a forged identification card, this can be very dangerous. Because it is not explicitly stated you fail to check its veracity. An example of an assumption would be that your favorite color is red, that you consider four pockets to be "plenty," that you like wearing jackets at all, and that the jacket will fit you.

Conclusion - A high-level judgment which can be used to make decisions. "This jacket is great" is a conclusion, and you might make a decision to purchase the jacket based on this conclusion.

Decision - An action taken on the basis of a conclusion. The more important and long-lasting the decision is, the more important it is that it be based on a sound conclusion which is itself backed up by plentiful, verified data.

For example, purchasing a house is a major decision, so a great deal of data should be collected by either direct observation (examining the house yourself) and from trusted, impartial sources (e.g. having an electrician check out the wiring). Based on this data you should have reached numerous solid conclusions including "I would enjoy living in this house," "I would be able to afford the monthly payments," "the price is fair market value," "the neighborhood is good" and so forth.

On the other hand, a decision of minimal importance would require very little data. For example, choosing to buy a hot dog from a street vendor may be based on three conclusions: the hot dog will probably taste good, it will satisfy your hunger, and it will not result in sickness or death. The data needed to back up each of these is minimal: the hot dogs smelled good, hot dogs have been known to satisfy your hunger in the past, and other people are eating hot dogs from the stand and appear to be suffering no ill effects.

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