The structure of logic; it's method of communication. Classical or traditional logic was first formulated by the Greek philosopher Aristotle, who developed rules of syllogistic reasoning. In it's most simple form a syllogism is an argument made up of 3 statements:

Major premise - "Only human beings have 46 chromosomes."

Minor premise - "This unknown blood sample has 46 chromosomes."

Conclusion - "Therefore, this blood came from a human being."

or

Major premise - "All riding horses have 4 legs"

Minor premise - "John owns a riding horse."

Conclusion - "Therefore, John's horse has 4 legs."
Logical arguments can also be mapped out using Venn diagrams. However, this deductive logic can be completely invalidated by the use of inductive logic.