Philinte is the Obi-wan to Alceste's Luke Skywalker, the Dumbledore to his Harry, the Jiminy Cricket to his Pinocchio. He dispenses wise advice to Alceste and the word "reason" is used around him so much that he's obviously meant to be the voice of reason. If Alceste followed his advice, he'd have a nice and honest wife, no lawsuits, and tons of friends.
This is where Molière kind of messes with Philinte's mentor role. You know, you're supposed to listen to your mentor. That's how they work. They tell you awesome things you should be doing and you do them, or at least try to do them.
The thing is, Alceste is not having it. He doesn't want a mentor. He doesn't want to listen to Philinte. He just wants to keep on doing what he's doing, even though that doesn't seem to be working out too great for him.
So can you be a mentor when your mentee refuses to listen to you? We're not sure. Philinte sure is trying though. Good luck with that, dude.