Lear & Oedipus: Lack of Knowledge
The notion of foolishness in Shakespeare’s King Lear and Sophocles’ Oedipus the King is very relevant and vivid. The two main characters of the books both exhibit distrust and foolishness. Although their individual manifestations of foolishness are quite different, still there is a similarity between them, because both Oedipus and Lear failed to recognize the reality around them, and continued to live in their own imaginary world. Therefore, regardless of their motifs and ulterior desires, both tragedy heroes can be easily called fools because they both lacked knowledge. Oedipus lacked knowledge about his family and his past, and when he was given chances to know who he was he refused to believe, and this was Oedipus’ major mistake in the book. King Lear, on the other hand, lacked knowledge about how wrong he had been ruling, and about the flattery that had been going on around him. He may be considered foolish, because he failed to tell the difference between the loyal, loving people and the fake, sinister ones. He also lacked knowledge about how he should live, and value genuine feelings. 
The phrase lack of knowledge is much more attributed to Oedipus than to King Lear. It was exactly Oedipus that truly lacked knowledge, because the truth was concealed from him for many years. Regardless of what wanted to hear or know, as long as he remembered himself he thought his father had been Polybus. Therefore it was natural for Oedipus to refuse to believe who his natural parents were. On the other hand, he behaved truly foolishly when he heard the truth more than once and still refused to believe it. The irony in this situation is that no matter how wise and kind the people may be, they can never foresee what is destined for them, nor they can change their individual path destined from above. In this regard, Oedipus is definitely a fool because he thought he could escape Corinth and avoid killing his father and marrying his mother. Unfortunately, by escaping the land with best intentions, he went closer and closer to fulfilling the prophecy. 
From the very beginning of the book, King Lear was behaving a bit weird. Since he was well in years, he was gradually losing his mind. There was a trace of foolishness in his decisions from the very beginning of the book. His minor insanity manifests in his failure to recognize flattery in his older daughters, and genuine love in the words of the youngest one. The tragic hero also behaved very haughty and ungenerously when he denied Cordelia, which testifies that he was a foolish king. The greatest mistake of King Lear, however, was that he failed to understand the real genuine human feelings and relationship. While being a powerful potentate, his decrees caused many deaths and grief, and he did not understand that he was also a man, the same as his valets and slaves. This foolishness of his caused the lack of knowledge, the inability to tell genuine human relationship from fake ones. Therefore, he could not even imagine what had been waiting for him after retirement. And even though Lear can be called a fool, he changed his worldview at the very end of the book, going mad at the same time.
Both Lear and Oedipus are fools in their own individual ways. Oedipus as compared to Lear was not responsible for the initial lack of knowledge about his natural parents and his real homeland. Oedipus, however, showed he was a fool when he though he could change his fate, and prevent the events destined to him. He also behaved foolishly when he refused to accept the evident facts. Lear, on the other hand, had total control over the situation, but foolishly did not amend it. Although he took himself for a great King, and thought he had valued the most noble characteristics in people, and thought he knew people around him very well, in reality he was surrounded with pure deceit. Lear was inundated with flattery and compliments, which obscured the real and natural qualities of human beings that must be valued and honored. Lear was a fool, and he paid the highest price at the end of the book for his foolish behavior.
In both Oedipus the King and King Lear the lack of knowledge and foolishness of main characters is a big issue. Both tragedy heroes lacked knowledge. However, Lear was responsible for his foolishness, and he understood this fact at the climax, when he encountered reality. Oedipus, on the other hand, was a kind person, not responsible for the lack of information, but he showed his foolishness and levity when he refused to accept the truth about him and his parents. In general, both characters can be called fools, but they are fools in different aspects.