The evolutionary context for a self-nonself discrimination.

This essay was written to illustrate how one might think about the immune system. The formulation of valid theories is the basic component of how-to-think because the reduction of large and complex data sets by the use of logic into a succinct model with predictability and explanatory power, is the only way that we have to arrive at "understanding". Whether it is to achieve effective manipulation of the system or for pure pleasure, "understanding" is a universally agreed upon goal. It is in the nature of science that theories are there to be disproven. An experimentally disproven theory is a successful one. As they fail experimental test one by one, we end up with a default theory, that is, one that has yet to fail. Here, using the self-nonself discrimination as an example, how-to-think as I see it, will be illustrated.