The act of assembling or recounting a sequence or network of facts and data1 leading to an inescapable, definitive conclusion.
Ostensibly, Engineers like us “reason” our way through problems to create designs. In this context, of course, “reason” implies a certain amount of logic in our thinking, which guides what data we pay attention to and how we interpret it. Philosophers refer to such rational processes as a form of “cognition“. The ability to reason with malice aforethought is a core concept in the mitigation of cognitive biases.
There are approximately as many theories on how we reason as there are philosophers2. See also inductive reasoning, deductive reasoning, and abductive reasoning for the three that are of the most direct use to System Engineering.
Footnotes