The question is: What is an "edge".
To me: an edge is an advantage you have (and that the majority doesn't), and you can exploit it and fully utilize it to beat your opponent (the market), more often times than not. Definitely not 50-50. Not even 60-40. Maybe 70-30, 80-20, 90-10 over some time period.
In a tennis analogy again:
Telling people to hit to ball over the net to the other side, and make sure the tennis ball doesn't go out of bound. That's not an edge. That's the basics of the game.
Telling people to run to where the ball is going so to position yourself to hit back. That's better. but that's is still not an "edge". Because most successful players can do that.
An edge that will lead you to win, as I see it:
* You can power-serve lots of aces like Andy Roddick. That's an edge.
* You can run cross-court like a maniac like Rafael Nadal. That's an edge.
* You can fight back under extreme pressure at the face of losing like Serena Williams. That's an edge.
* You can split your legs like Kim Clijsters to catch a ball. That's an edge.