The form can be revealed by substituting symbols for the content of the claims in the premises and conclusion. There are many basic valid forms of deductive argument. There are, unfortunately, many more invalid argument forms. Some of these have names and are called fallacies because they give the illusion that they are valid. We'll look at three such forms shortly, but first we must explain what it is that makes deductive argument forms valid or invalid.
Arguments are valid or invalid because of their form .
Argument A has a valid form. Thus, the conclusion is true if both premises are true. The street is wet. Thus, it rained. It is obvious that, for people engaged in technical or professional communication, having some understanding of logic will be crucial.