to khemix,
Thank you for the response.
I am not sure whether the history of logic, that is, some establishment of when or where or by whom, it was first employed, is important. I'm not sure that such a question is not just a wild goose chase.
The more important question is set up by the presumption that our thinking, reason, has anything to do with logical argument. There is the prevailing assumption that when we talk about clear thinking we are talking about thinking logically. I wonder about that. So, thinking may have been around for a long time...that would be another question. However, there is the further question of just how people came to believe that clear thinking was a matter of logical argument.
I suspect that the assumption about logic has to do with the argument going on at the same time about whether we think of God monotheistically, or polytheistically, whether God has to do with a point or view, or whether the Gods have to do with the controversies of this life, in the world. I want to connect up the argument that reason is a certain way with the argument that we have to imagine God in some certain way.
Furthermore, when you read Plato and Aristotle, you find out that before there was any consensus that thinking or reason was a matter of logical argument, there was a prior dispute between the sophists who apparently championed rhetoric, and others, presumably Socrates and his allies, who championed Logic against the Sophists. I think this goes to my point that reason being understood as a matter of logical argument is not something we cannot question. There are those even in Plato's dialogues who would have questioned whether reasoning had to be logical.
You pointed out that it was the Greeks who were concerned to analyse arguments, to write about them, to develop theories like Aristotle's or the Stoic's, and so on. I have to say that these may just be technical developments that are made after some idea or justification has already been made. So Benjamin Franklin might have discovered electricity, say, but it was Edison who developed the light bulb, et al, and made technical developments about that discovery. I'm just saying that the developments we see in Aristotle do not amount to the discovering of logic, in the same way that developing the light bulb does not amount to discovering electricity.