Since first teaching logic in middle school, I have used the following working definition of reasoning and have found it quite helpful. “Using knowledge one has to discover new, previously unknown knowledge.” It comes from Martin Cothran’s Traditional Logic I. Some progressive pedagogies place a heavy emphasis on understanding before memorization and sometimes to the exclusion of it. I disagree with this emphasis, for understanding is the fruit of reason, and reason cannot be conducted if there is not pre-existing knowledge in the mind. One must have memorized facts to reason to thorough understanding.
There is a difference between reading an argument on a page or experiencing it as an experiment and owning it in one’s mind. Comprehend might be a better word—grasp a truth with the mind. So long as we do not require our students to memorize the basics, we prevent them from truly owning understanding, for all their facts are “borrowed.” I see this in the children of poverty with whom I have worked. They are required to memorize very little, so in the learning process, they must do more than the child who has memorized facts. They must reason and hold information in working memory, recalling it from a page or an experience instead of from their own long term memory. This requires intensive effort—the very kind of effort that socio-economically disadvantaged students struggle to give.