We began this course by looking at different, everyday sorts of arguments. In an effort to better understand reasoning, we then asked what features of a good argument distinguish it from a bad argument. In a valid argument, IF the premises are true, THEN the conclusion must be true.
Validity is truth-preserving.
If one begins with a valid argument and has true premises, then one will always end up with a true conclusion. In other words, it is impossible for the conclusion to be false while the premises are true. The validity of an argument is thus guaranteed by its form and does not depend on its content. This is the first approach that we learned, though it is not specifically listed as such in the text. To apply this method, simply imagine that the premises are true and ask yourself if it is possible for the conclusion to be made simultaneously false.