THE TORAH RELATES how Esau came in to request the blessings from his father Isaac, not knowing that Jacob had already received them. When Isaac realized the trickery that had occurred he “trembled in very great perplexity”.
I once heard a wonderful comment on this.
At the beginning of the chapter we find that Isaac became blind. One of the explanations presented by Rashi is that Isaac was stricken with blindness in order that Jacob be able to carry out the plan to take the blessings. But why couldn’t Jacob obtain them without having to resort to trickery, and why did Isaac have to become blind?
The answer is that Isaac truly believed that it was God’s will that Esau receive the blessings, and no reasonable argument could ever convince him otherwise. When Esau walked in, however, Isaac realized how God had been working against him from the outset. At that time he realized how mistaken he had been all along, and that only by becoming blind could his obstinacy be circumvented. This recognition is what caused him to “tremble in very great perplexity.”
A lesson in foregone conclusions.
Rambam  writes that just as one naturally likes that which he has become accustomed to and is attracted towards it, so it is with the opinions of man to which he has been accustomed from his youth; he likes them, defends them, and shuns opposing views. This, he contends, is a cause which prevents men from finding truth, and which makes them cling to their habitual opinions. A person might even come to interpret a passage of the Torah or a Midrash contrary to its original intention, because he does not wish to modify his original opinion to serve the truth.
Sometimes it may be appropriate to read things literally, sometimes allegorically, and sometimes it might even be appropriate to dismiss something altogether as incomprehensible or irrelevant. The important thing is to be mindful that obstinacy is the greatest stumbling block to truth. We can only hope that by not jumping to conclusions and sticking to them, the day will never come when we too “tremble in very great perplexity.”
 Guide for the Perplexed 1:31