Last week gave Person of Interest viewers their first look at Samaritan, the competing surveillance system that threatens to bring down The Machine – Harold, Reese, Shaw and Root along with it. I posted my thoughts right after the episode but want to take a closer look at how the two systems differ.
This is the last we’ll see of The Machine this episode. Or is it?
Samaritan’s white launch screen is a 180 from The Machine’s black background pictured above:

A look at the differences and similarities in how they identify subjects. The biggest thing to note here is how Samaritan is given mandates and targets. Harold programmed The Machine to prevent using it exactly that way.
You can see more of Samaritan’s organized vertical interface versus the way The Machine scatters information about the screen:
A look at the differences as they appear when Samaritan and The Machine search their archives:
The systems use opposite ways of marking targets:
This shows that for all their differences, the two systems operate with the same fundamental technical skills:
Here is the key difference the show has been driving home to its viewers: The Machine only identifies threats, Samaritan finds them and tells you what to do with them.

Remember when I said we might see The Machine later in the episode? I think this is it at work protecting Harold. Wherever it identifies him, it shuts down the feeds so Samaritan cannot see him. Note that it doesn’t give the same protection to anyone else.
