Socrates and Plato together clearly illustrate the change that came over Greek thinking.
Socrates championed rationalism, an idea that had been slowly percolating through the Greek consciousness. He also refined the concept of the long verbal sequence, (here’s an example of his style) but it was Plato who tidied up Socrates’ ideas and presented them in writing. In the process, I have little doubt, Plato must have tightened up Socrates’ logic. The end result was a series of long dialogs presenting chains of logically connected sequences. Socrates begins the dialog by proposing to examine some interesting question, then meanders through an intricate maze of logical connections, until he arrives at some entirely surprising result.
The significant point here is the length of the sequence. There had been philosophers before Socrates, and they had many useful and interesting insights, but it is not until Socrates that we see any success in attempting a long, careful sequence of steps to arrive at a conclusion. Here we see reason beginning to assert itself for the first time. Unfortunately, the Socratic dialogs suffer from both of the weaknesses of verbal reasoning. First, they are so long that the reader can readily lose his logical bearings. By the time the end of the dialog has been reached, the reader has the feeling that he is inside one of those M.C. Escher drawings in which each individual step seems reasonable, but the whole of the picture is nonsense. Indeed, some of the Socratic dialogs reveal under careful analysis a logical structure that is less than reliable.
The second weakness of the Socratic dialogs is their heavy reliance on the precise nuances of meaning of certain Greek words. This is obvious to anybody reading a translation; some of the conclusions drawn make little sense when expressed in another language.
Here’s an example, taken from Symposium:
“Then now”, said Socrates, “let us recapitulate the argument. First, is not love of something and of something too which is wanting to a man?”
“Yes”, he replied.
“Remember further what you said in your speech, or if you do not remember I will remind you: you said that the love of the beautiful set in order the empire of the gods, for that of deformed things there is no love -- did you not say something of the kind?”
“Yes”, said Agathon.
“Yes, my friend, and the remark was a just one. And if this is true, Love is the love of beauty and not of deformity?”
“And the admission has been already made that Love is of something which a man wants and has not?”
“True”, he said.
“Then Love wants and has not beauty?”
“Certainly”, he replied.
“And you would call that beautiful which wants and does not possess beauty?”
“Then would you still say that love is beautiful?”
Agathon replied: “I fear that I did not understand what I was saying.”
This line of reasoning might seem confusing in English. One of its tricks lies in the references to “love of something”, which in English means “love towards something” where in Greek it means “love as part of something”. In Greek the argument carries more force than in does in English, but the fact remains that the logic is certainly not airtight. This is reason, but it is not logic.
Thus, Socrates and Plato made two huge steps forward: in effect, these two perfected the invention of rationalism and reason. The stage was set for Aristotle to turbocharge reason with the syllogism, thereby creating logic, the powerful driving force of Western civilization.