Reason (Theoretical and Practical), Rationality and Reasonableness. On Limits, Similarities and Differences

The human being always seeks to explain what exists and happens around him, likewise, he always aspires to determine the morally good. This generates in him the need to find certainty in the knowledge that acquire in that search and objectivity in that practical-moral determination. Once the supernatural and the divine results unsatisfactory foundations for him, he can only appeal to his reason as the last resource, but what make the reason be constituted in that ultimate foundation? To what extend can effectively the reason satisfy that search of objectivity or certainty? What does the distinction between theoretical reason and practical reason answer to? When and why is something said to be rational or reasonable? What resembles, differentiates and determines the scope and limits of rationality and reasonableness? These are questions that are sought to be answered in this work following a methodology that aims to intuitively guide the reader's own reasoning.