A logical form is essentially a language formula designed to reveal the essentials of a true statement. Methods of thought that employ the logical form include deductive and inductive reasoning, logical analysis, and retroduction. A logical form is made by boiling a statement down to essential components, using quantifying variables for the active parts of the sentence. When the statement is an argument, it can be called the argument form. The development of this method is attributed to the Greek philosopher Aristotle.
One of the main advantages of this method is that it is a means of examining the basic parts of an argument to determine whether its form allows the possibility of the argument being true. It's not a foolproof method though; a logical form can prove that a false argument is true if one of the argument's premises is false, so it's not safe to assume that an assertion is true based only on logical form. When applying a logical form to an assertion, it is important to consider whether the assertion is meant to apply overall or just in a particular context, because a statement can be true in some situations even if it is not true in all situations.
The logical form is created by turning the parts of a statement into components that are represented by variables. In the statement “All candy is dessert, and all dessert is wonderful," the form would be represented as "All C is D, and all D is W." Once it is reduced to variables, it is treated much like a mathematical statement. This shorthand pulls information that is irrelevant to the contextual truth of the statement out of the way, allowing conclusions to be made from the form of the statement rather than the content. From this statement, it can be inferred that C, being D, is also W, so all candy is wonderful. Introducing the statement "All pie is dessert," or "All P is D," to the previous statement would lead to the conclusion that all pie, being dessert, is also wonderful.
Breaking down arguments into their basic components often reveals that such arguments follow one of the recognized logical forms of argument. These forms help identify whether an argument is valid, sound or invalid based on how the statements leading to a conclusion are arranged. Common valid argument forms include the dilemma, the proposing mode and the removing mode. The many logical fallacies which create the weaknesses in invalid arguments include using personal attacks, generalizations or appeals to authority to make the stated case.