According to Vincent Ruggiero's Beyond Feelings: A Guide to Critical Thinking, the term logical fallacies refer to the concept of, "making errors that impairs reasoning and thinking," (87). The concept of recognizing when one is making errors in thinking may be difficult or unclear to see, so it is common for some to make the mistake of committing logical fallacies. An example of illogical reasoning and thinking is present in William Shakespeare's play, Othello, where Iago, who is Othello's most trusted advisor, plans and acts out his revenge on Othello, who is the good and noble general, because he is jealous over a promotion he did not get. Iago helps initiate Othello to commit logical fallacies and think uncritically by making unwarranted assumptions, automatically rejecting others, and making hasty conclusions when presented with the issue of his, "cheating wife," Desdemona. Due to Othello's unwillingness to recognize his illogical reasoning and errors in thinking, for he lets his emotions cloud his judgment and becomes vulnerable to manipulation and corruption, which then ultimately leads to his downfall.
Firstly, one of the logical fallacies that led to Othello's downfall is the error of unwarranted assumptions. Ruggiero defines the fallacy of unwarranted assumptions as, "ideas that are merely taken for granted too much rather than produced by conscious thought," (99). In Othello's case, he makes an unwarranted assumption when he presses and trusts Iago for answers about what he thinks about Cassio, his lieutenant, and Desdemona, his wife, meeting and talking together: .
I heard thee say but now, thou lik'dst not that,.
When Cassio left my wife; what didst not like?.
And when I told thee he was in my counsel.
In my whole course of wooing, thou criedst, 'Indeed!' (3.3.109-112).
Although the reader knows it that Iago is playing and tricking Othello into believing his claims, Othello trusts Iago's word of this situation, and which begins his doubt of Desdemona as a loyal wife.