"The Philosopher's Stone" is a pivotal, fun, adventurous, exciting, outstanding, revealing, wonderful character development, cleverly plotted, nerve-wracking, and a very painful to watch episode.
It is pivotal to the story line, because at this point the story introduces the major plot lines for the remainder of the series. Well from this viewer's perspective - who has only seen episodes 3 through 8 Introduced are Scar and the Philosopher's Stone, which I expect will dominate the series for quite awhile. Scar becomes the recurring bad guy, while the stone is the object that may restore Ed and Al.
The characters go through some hair-raising and nerve-wracking moments but in the end it is exciting and provides us with character development and insight. Winry comes to the city to join Ed and Al, but gets caught up in Ed's current case. Ed because of his heart can't accept his current assignment and like a kid or a person with great integrity resigns. Ed takes on the cause of who is killing people and maybe Nina.
As always our gifted hero gets to the bottom of at least part of the truth. While he doesn't discover who killed Nina, he does solve the on-going brutal murders of pretty women. The question, though, remains who killed Nina and how?
Through this adventure we see deeper insight into Ed and Al. Al is hollow. In this world Al has lost most of his emotions, because he doesn't have a body. He longs to be a child again, to feel, to play, to love, to hate, to be joyful, and to be sad. He looks to Ed to suck it up and do what is necessary to get their bodies restored. Ed fights his responsibility to Al, because it means losing part of his will and integrity. In the end, though, Ed capitulates by going back to being a state alchemist, but on the condition (to the Major) he can do what is necessary to restore himself and Al. We also discover Al's condition is a secret because the military would take him away to examine him as an example of human alchemy.
Those viewers who also have been reading the Dexter series by Jeff Lindsay or watching Dexter on Showtime will notice similarities between a character in this episode and the Dexter storyline. Which story came first? It seems Fullmetal Alchemist has a much earlier copyright when you consider the anime ((c) 2003) comes from yet even earlier work. I suspect it turns out to be two great minds thinking very much alike, though.