Humans are incredibly easy to manipulate. We make comparisons all the time, using what we don't want to decide what we do want. By skewing the options, you can control what people decide is the most favorable choice. This happens all the time and we don't even realize it. It also happens in literature, especially in Oedipus. If Laius hadn't been so quick to believe in the prophecy, he wouldn't have set the chain of events going that led to the prophecy's fulfillment. If Oedipus' adoptive parents had simply told him he was adopted, Oedipus wouldn't have felt the need to run away and unknowingly fulfill the prophecy. The oracle never told Laius the entire story. If Laius had kept Oedipus, Oedipus wouldn't have killed him or married his own mother. This all could have been avoided if Laius had been given every choice available to him.