On Wednesday, Homeland Security Secretary Michael Chertoff did one of those periodic web chats the White House hosts, this one on border security. The whole thing was pre-digested and tightly choreographed, of course, but one of Chertoff’s answers succinctly expressed one of the main areas of difference between the enforcement side and amnesty/guestworker side. When asked about the “temporary” worker program, part of his response was:

When I speak to the need for a temporary worker program, I often use the analogy of a river dam. If you are going to dam a river, it is much easier if you channel water in areas where it can be productive and take the pressure of the dam. In the immigration context, channeling foreign workers to jobs that Americans won’t do and matching them with willing workers is a sensible way to ease the pressure of the immigration system and meet our country’s economic needs.

The dam analogy only works, though, if you think that immigration is a force of nature, an unstoppable phenomenon that we’d better accommodate ourselves to. But it’s not like a river, flowing downhill whether we like it or not; it’s more like siphoning gasoline through a hose — you have to get it started, and you can stop it, if you decide to. See more here.