Friday, September 03, 2004

The Three Types of Reasoning

by Asim Jalis

Continuing with the thoughts from the previous essay, there is a third type of reasoning. Let's summarize the first two types first. The first kind of reasoning is sequential reasoning, where each assertion follows the next through a chain of implication. The archetype of this kind of reasoning is Commander Data from Star Trek. The second kind of reasoning is generalizing and specializing. Here specific examples are seen as concrete manifestations of general ideas, and general ideas are extracted from specific examples. Things are connected to each other in unexpected, unobvious and surprising ways. The focus is on the connections rather than the nodes. An archetype of this kind of reasoning might be Einstein. Another example of someone who uses this is Clayton Christensen. The third kind of reasoning is centered around "why". Why did this happen? Why did this person behave in this way? For example, when we talk about the value proposition we are talking about this kind of causal reasoning. The archetype of this kind of reasoning is Sherlock Holmes. Holmes moves from effects backwards to the causes, always asking why about everything. Toyota and Taichi Ohno's process of getting to the bottom of defects by asking why five times (the five whys) is another example of this. The boundaries between these types are fuzzy. Many problems require a combination of multiple types of reasoning. In general the second and third kind of reasoning are mechanisms for discovering or recognizing new ideas. The first kind of reasoning is mostly used for verifying that a chain of reasoning suggested by a discovered pattern or by a 5 whys investigation, is valid.