The god Apollo through his mouthpiece, the Oracle of Delphi, tells Socrates' friend that Socrates is the wisest man in Athens.  After this is reported to the then scientist Socrates, he begins to doubt the judgement.

An all powerful god has reported a fact and the reciever of this fact doubts the message.  To doubt the message of a god is to doubt the power and abilities of that god or to doubt the god himself. 

Of course, the pre-Socratic Socrates, that is to say, the scientific Socrates and not the philosophic Socrates may not have believed in God or gods.  This "fantastic" and "incredible" decree was spoken by an Oracle, but speaks to Socrates' ego and seems to point to something further than himself.  The god seems to challenge Socrates' reason.

Why would Apollo have chosen Socrates, after all?  He was just another sophist?!  He was just another person who questioned the whole and looked beneath the earth and above the clouds for answers.  He was  an Athenian scientist. 

With his head full of wonder, Socrates set out to prove this "god" wrong by finding someone who is wiser than him.  Athens, being the pinnacle of civilaztion, would be full of wise people.  He went to the Athenian market and found people who seemed to know things. 

Artists, politicians, artisans, sophists and so on were interviewed by Socrates' sharp wit. He soon discovered that these "experts" surely knew about their field.  However, when the questions that he asked led to higher or different levels of knowledge Socrates found that they guessed as they pretended to know.  They were ignorant while they pretended to be wise.  This made them unwise.

They knew their place found within the whole, but were ignorant of the whole.  They pretended that their piece of the whole was the whole or was at least the most important part of the whole.  "How can they know that their knowledge is THE knowledge unless they know where in the whole of things their knowledge belongs?" Socrates might have asked from time to time.

As their ignorance surfaced, Socrates saw that he was wiser than those people he spoke to because they pretended to know, and did not really know, while he knew that he did not know.  He knew this by the simple fact that a god had declared him to be the wisest while he doubted the Decree.  The fact that he searched for an answer revealed his ignorance.

Actually, the very fact that Socrates doubted the god's decree seemed to prove the god correct.  As Socrates attempted to be impious by doubting the word of God he was proving God correct the entire way.  And yet, he could not know if he was the wisest until he had interviewed everyone who might be wiser than him.  Socrates' radical doubt would not allow him to interview A FEW people to assure him that the god's decree was correct.  He had to interview everyone. 

Socrates's doubt compelled him to continue his questioning until he had proven the god to be either right or wrong.  The more he questioned the more sure he was in his answer, but that nagging doubt would not allow him to stop his questioning until the job had been completed.

Socrates also inadvertently showed himself to be pious by showing how weak human reason is as it attempted to challenge the gods.

By asking his questions, Socrates is assuming, incorrectly it seems, that Apollo had incorrectly identified him as the wisest of the wise.  The more he questioned the more he proved his doubt to be unfounded and Apollo to be correct.  But his doubt insisted that he continue his quest until a true aswer had been reached.  While attempting to prove God wrong he continued to prove God right.  By attempting to act impiously he continued to give credence to piety.  By the use of his keen reasoning abilities, Socrates showed the weakness of reason.  Socrates was a failure and a success at the same time.

Reason would seem to point to the fact that Socrates was not pious and yet all of the evidence points, argueably, in the opposite direction.  No final answer can be attained by the use of reason.  It seems that only faith, one way or another, can give that final answer to the Socratic quest.

Reason can investigate a role within the whole, but it seems that it cannot investigate the whole.  For it to investigate the whole it would have to step outside of the whole for a safe vantage point.  This seems to be impossible.  Reason seems to devour itself or dilute itself as it investigates itself.  Reason then reveals to itself how limited it is within this "whole."   As stated in another post, this usually leads to what the Geico caveman mentions as an "existential meltdown."

Socrates did not meltdown however.  He converted from a scientist/sophist to a pious philosopher.  A philosopher who investigates, but a philosopher who also leaves well enough alone as he investigate.  He cannot replace other people's opinions with knowledge because he doesn't possess true and permanent knowledge himself. 

He replaces bad opinions with better ones and he speaks to the level his audience requires of him.

Socrates can investigate pieces of the whole, but cannot get outside of the whole to investigate it.  He is ignorant of the whole as the whole (even the existence of a whole), but is open to the possibility of a whole. Socrates becomes a philosopher who still doubts the god's existence, but since he has no answers of his own cannot fully argue against the gods just as he cannot fully argue for the gods. Socrates, through Apollo's decree and his own doubt, has become as pious as a philosopher can be.