Since I believe that many of Wikipedia's philosophy related articles need improvement, I don't take reversing other editors' contributions lightly. There have to be multiple reasons, but mainly whether the contribution vandalizes the article, makes the article philosophically at odds with accepted professionally published sources, or less readable for casual visitors.  

 While I am delighted to encounter another person who takes as much pleasure from Plato's works as I do, I'm forced to oppose your edits on all of the above grounds. Of course, if you can find a peer reviewed professional article to support your addition, just as you have stated, then I will back off without further conditions. That cannot be your previous reference to Cooper's Introduction to the Phaedrus which is open in front of me. He says nothing about madness, (Phaedrus 244a ff). 

 Naturally, these are all based on my personal judgment. However, according to Wikipedia rules for resolving editing conflicts between editors {WP:DR}, you may not insist on changing the article over the other editor's objections, as you are doing. You need to have a consensus of other interested editors first. You don't have that. 

 Also, please have a look at {WP:NOR} "No original research" for guidelines.