A reader writes:
Israel's rationale is not that hard to figure out. Check out Rosner over here. Here's the summary paragraph:
So - the IDF and Israel's leaders have three goals in launching this ground war: First, they want to make Hamas pay a price that will force it into a renewed ceasefire. Second, they must prove to the Arab world that Lebanon 2006 did not turn Israel into a country afraid of war. And third, they must engender renewed Israeli confidence in the country's armed forces.
As to the first goal, we don't know how Hamas will respond, i.e., whether it responds to deterrence. Israel has never gone after Hamas. That was Pollak's point to you over here. Money quote:
Nobody knows at this moment whether Hamas is deterrable. The question depends on whether Hamas actually intends to fight to the last man and on the efficacy of the IDF's ground war. But surely it is also true according to just war theory, no less that the sovereign state of Israel, in an attempt to protect its citizens, is allowed to discover whether deterrence is possible. I note that since August 2006, Hezbollah has been awfully quiet on Israel's northern border; and that since 1973, so have Syria and Egypt.