A central tenet of Othello is the concept of right judgement, and to always use it when making decisions. The renaissance definition of right judgement can be illustrated by the so called "hierarchy of right judgement." Governing all is reason, which includes understanding and will. Below reason are common sense, memory, and imagination. Finally, at the bottom are the 5 senses, emotions, and passions. In order to judge rightly, it was believed that reason had to govern all else. Right judgement could never occur if only one item was relied upon to make the decision. In Othello, Shakespeare uses this concept to demonstrate how right judgement occurs, and the consequences when it does not.
The first scene in which right judgement is used is when the Duke makes a decision as to what should be done about the expected Turkish invasion. He does not immediately act on the information he receives, instead, he thinks out the steps logically. When he states, "I do not so secure me in the error, but the main article I do approve in the fearful sense (I 3 12-14)," he is showing that he will not rely solely on the information he is receiving, but also use common sense, memory, and understanding, and therefore judge rightly. Only after right judgement was used did he take action, and therefore avoid disaster. The Duke is a model of right judgement who can be compared to other characters in the play to show their weaknesses and shortcomings.
In the same scene, right judgement is demonstrated again by the Duke, when he is faced with the mater of Othello marrying Desdemona. Initially, the Duke rejects wise judgement by promising to allow Brabantio to sentence whoever had done this to whatever punishment he saw fit, without analyzing the situation further, and without even knowing who that man was. However, upon assessing the situation more, he realizes the consequences of not using right judgement, and, after hearing all sides of the story, tell Brabantio to "Take up this mangled matter at best. Men do their broken weapons rather use than their bare hands (I 3 199-201)." Later on, he gives Brabantio wise advice when he tells him that "to mourn a mischief that is past and gone is the next way to draw new mischief in (I 3 234-235)." This further shows that the Duke is indeed a wise man who employs right judgement in all matters, and therefore is successful in those matters.
The right judgement of the Duke is contrasted with Othello's poor use of right judgment in Act 2, Scene 3. Othello arrives at the incident and immediately wants information. He allows his emotions to overrun his logic, saying "My blood begins my safer guides to rule, and passion, having my best judgement collied, assays to lead the way (II 3 219-221)." He admits that any decision he makes will be clouded by his passions, and indeed his decision is made poorly. He does not allow himself to learn what really happened, and although Cassio was at fault, he did not allow for other possibilities. He heard information from one source, and a corrupted one at that, and was satisfied with that. Right judgement dictates that he should have found out the whole story, like the Duke did, and not have allowed his decision to be made by his emotions.
Another incident in which Othello shows poor judgement is when he allows Iago to persuade his thoughts in Act 3 Scene 3. He allows himself to be led into denying reason and instead rely on imagination and what Iago tells him. However, there is a moment where Othello shows reason, when he says "I'll see before I doubt; when I doubt, prove; and on the proof, there is no more but this: away at once with love or jealousy (III 3 221-223)." Here Othello is demonstrating that he will not allow himself to be run by anything but reason, and that he will act on reason alone. However, his mind is quickly changed by Iago's tricks, namely by pulling on Othello's deepest fears. Once again, and not for the last time, Othello allows himself to be ruled by passions and emotions rather than reason and understanding.
The final scene where right judgement is shown is the