<P> Reason is a type of thought, and the word "logic" involves the attempt to describe rules or norms by which reasoning operates, so that orderly reasoning can be taught . The oldest surviving writing to explicitly consider the rules by which reason operates are the works of the Greek philosopher Aristotle, especially Prior Analysis and Posterior Analysis . Although the Ancient Greeks had no separate word for logic as distinct from language and reason, Aristotle's newly coined word "syllogism" (syllogismos) identified logic clearly for the first time as a distinct field of study . When Aristotle referred to "the logical" (hē logikē), he was referring more broadly to rational thought . </P> <P> As pointed out by philosophers such as Hobbes, Locke and Hume, some animals are also clearly capable of a type of "associative thinking", even to the extent of associating causes and effects . A dog once kicked, can learn how to recognize the warning signs and avoid being kicked in the future, but this does not mean the dog has reason in any strict sense of the word . It also does not mean that humans acting on the basis of experience or habit are using their reason . </P> <P> Human reason requires more than being able to associate two ideas, even if those two ideas might be described by a reasoning human as a cause and an effect, perceptions of smoke, for example, and memories of fire . For reason to be involved, the association of smoke and the fire would have to be thought through in a way which can be explained, for example as cause and effect . In the explanation of Locke, for example, reason requires the mental use of a third idea in order to make this comparison by use of syllogism . </P> <P> More generally, reason in the strict sense requires the ability to create and manipulate a system of symbols, as well as indices and icons, according to Charles Sanders Peirce, the symbols having only a nominal, though habitual, connection to either smoke or fire . One example of such a system of artificial symbols and signs is language . </P>

What is one important purpose of an opening argument