Reasoning can be defined as the practice of discovery or formulation through the exercise of logical thought. Understanding of human reasoning pattern is important to make the system design more logical and user centered. Established models of reasoning or decision making have been developed through the use of logic. Reasoning is also important to cause effect relationships. For example, if users/ consumers select a particular product with particular design attributes, designers may conclude that design features are the reason for selection off that product. A brief description and example of four different kinds of reasoning will explain how human put logical thought into his/her practice.