(Noun)
1) The process of thinking and making arguments in a rational, coherent, sensible manner;
2) Way of thinking (of someone),
particular way in which they made arguments and arrived at conclusion;
3) The use of reason.
It's the quality given to
human beings by nature, although not all humans opt to use that valuable aptitude. Many people believe in their reasoning, but their beliefs turn out to be wrong and
consequently their reasoning about their belief of reasoning of reasoning turn out wrong as well.