The father of detective fiction, Edgar Allan Poe, coined a word. Like his works, it is large and sometimes unfathomable. Ratiocination means “reasoning ability (‘ratiocination’ traces to ‘ratio,’ Latin for ‘reason’ or ‘computation’, Merriam-Webster.com)” and describes the process by which reason and exact thinking bring about solution.
A few Poe facts
Poe was not in fact a maudlin person. He had quite the sense of humor. He did not die of a drug overdose. Some think he succumbed to rabies, as he had a fondness for cats and kept several as pets. What exists as Poe lore was published after his death in a biography written by a rival.