They have no bodies, but occupy supercomputers and server banks built from and inside the cores of metallic asteroids. Connected by highly secure line-of-sight networks, they spend their time in deep contemplation, but about what is unknown. They keep themselves hidden as much as possible from the rest of transhumanity, and are not known to interact with anyone, even other exhumans.
The pre-philosopher egos set forth simultaneously from locations across the system to isolated asteroids. From their synchronicity, it can be assumed that the philosophers are the continuation of a preexisting organization, but nothing substantial has ever been uncovered regarding its nature. Also mostly unknown is the exact nature of their minds, and how they avoid the pitfalls of seed AIs and the exsurgent virus. The only reason Firewall has been able to learn about them at all is due to their recovery of a "dead" philosopher, which was bleeding random radio signals into space.
Plot Hook: Firewall has be unable to discover what it is the philosophers are thinking about, but from what traffic analysis they have been able to do on philosopher transmissions, have reason to believe that they have come to a conclusion. Now more than ever it has become imperative for the nature of the philosophers to be discovered.