The theme of Fox's new Friday night scifi is the nature of what it means to be a human being. The principle it's based on is the ancient concept of dualism -- one I consider false but defensible.
Echo's personality has been surgically removed so she can have new ones implanted. This is meant to be a showcase for Eliza Dushku's talent, which it isn't quite yet, though she's a satisfactory actress. This is partly because the 'blank slate' of Echo is still too mich of a cypher. Moreso it's because she was given physical crutches to show the character she plays, in the form of glasses &an inhaler.
Cromartie, of course, started out without a personality, unless you count being a soulless killing machine. Now he's developing one, into which Agent Ellison is attempting, perhaps without hope, to imbue some sort of morality, or as he called it the "First Ten" directives. In both shows the body is the vehicle for th 'I'. Echo's body is used to deal with the conflicts of an ensemble of characters, while Chromatie and Cameron's chassis are simply platforms for the chip that contains whatever a Terminator has in place of a soul.
It's hard for us to see it any other way. Early references to mind/body dualism was recently found in Mesopotamia dating from 1000 BC or so, but doubtless it's a lot older than that. This is in spite of the fact that a mind without its body has never been observed, while a brain-bearing body without a mind can live, but not to any particular effect.
Those of you paying attention have noticed that I've lazily been making no distinction between concepts like 'mind,' 'soul,' 'personality' and the universal human concept of the 'I'. That's not because I am not sure those can be as easily separated as most people think, though I'm pretty sure they can't, like the different words blindfolded men use to describe an elephant. More important is that television lacks any method to distinguish how a person acts from who he or she is, and few enough even to distinguish that from how he or she looks. When Echo comes out of the 'treatment' chair and we need a key that she's still the hostage negotiator, the first thing she says is "where are my glasses?" Meanwhile, Chromartie's body could have been reconstructed into anything (why don't they make Terminators look like innocent little kids, helpless old ladies or poodles?) But of course it was given the same stolen B-movie actor's face that belongs to the real-life TV actor Garret Dillahunt. This is partially because there's no reason to replace an actor who's a pretty good killer robot, but more importantly because we wouldn't recognize him otherwise as Chromartie.
Though none of these themes are new to sci-fi, the popularity of these shows will give us qa hint whether the future of the genre will be, as I suspect, a deeper exploration into the interior questions of the nature of the 'I.' A confluence of new understandings of the nature of the brain, continued advances in AI tech an increasing awareness of the limits of of where we can explore physically (Mars ain't the kind of place to raise your kids) is going to increase our interest in where we can go in the human head.
Hopefully we will not be so enthralled as Topher Brink, played by Fran Kranz, the real show-stealer of the first episode. Brink is the joyfully amoral super-geek, so enthralled by what his tech can do he's pulled completely beyond any sense of right &wrong. It was people like him, I'm sure, who created the hydrogen bomb. Dollhouse confronts us with the thought of what such a person might make of the potentially deadliest weapom of all: the human mind.