This is not a flick to see lightly for entertainment.
A genetically engineered virus that was supposed to cure cancer wipes out 90% of the human race instead, and turns most of the rest into mutated, rabid, aggressive, vicious, and very hungry monsters who only come out at night. Will Smith is a medical researcher who (with his faithful German Shepherd, Samantha) is the only survivor left in New York City and, for all he knows, the world. He is trying to build a vaccine and cure from his own immune blood--but it may already be too late. There are a couple of philosophical issues of interest to Christians that are central to this story. First is the ethics of genetic engineering and "playing God." Scientific hubris definitely takes a hit--and yet science, which is the cause of the problem, may also be its only solution. But will it be science alone? No. And thereby hangs a tale--which brings us to the second issue.
Very important also to the plot is theodicy, the problem of evil (think of C. S. Lewis's The Problem of Pain). Smith's character eventually meets another survivor. She is a believer who is looking for a colony of survivors. She believes it is out there because "God told her" it was. How, Smith wants to know. "The world is so silent, now," she replies. "If you listen, you can hear Him." Smith has lost his faith because of the devastating plague, and they have a short but intense argument about theodicy. He seems to win on points, but it turns out that the colony does exist and his meeting her is the only way his cure can reach it with hope for the future of humanity. They are attacked by the mutants, and Smith sacrifices himself so that she can reach the colony with the cure. "What are you doing?" she asks him at that point. "Listening," he replies. And so she does find the colony and the human race is presumably saved. The role of faith and the means of its validation remind one somewhat of that Mel Gibson film of a few years ago, Signs.
I have both a positive and a negative reaction to all of this. On the negative side, the woman's faith is in a very vague God who apparently speaks only subjectively. It may not even be the Christian God; if it is, it is a very subjective Pentecostal or Charismatic version of Him where revelation comes not objectively through Scripture but only subjectively through an inner voice. People in the real world who "listen" to that inner voice often hear all kinds of idiocy from it, much of it contradictory to Scripture. So let's not get too excited about "Christian" themes in this movie. Some of us are too eager to read explicit Christian content that may not be there into any film that isn't positively hostile to faith. A work of art does not have to be explicitly Christian to be appreciated for raising in a helpful way issues worth thinking about.
On the positive side, faith in God is shown not to be bogus. There are many positive insights either made or suggested. Even Smith (in his atheist period) says, "God didn't do this [evil]; we did." He means at that point partly that only we humans, specifically scientists, specifically himself, can fix it. The optimistic humanist hope that "I can fix this!" echoes throughout the picture, only to be shown to be a false hope. It turns out that Smith's efforts would have been in vain without what looks an awful lot like Providential intervention.
Most interesting of all then is the idea that Religion and Science need each other. Either alone would have failed to save humanity. The believer couldn't have done it without Smith's science; he couldn't have done it without her faith. Each comes to understand and appreciate a need for the other. A more interesting and possibly helpful way of thinking about how Religion and Science ought to relate than those one sometimes hears from either side is then suggested by the story, one potentially consistent with reformed themes such as common grace and the cultural mandate.
Of the films I have seen this year, this one should be one of the more interesting to Christian thinkers. Its answers are not without flaws, but it raises good questions in a helpful way. But seriously, don't see it unless you are prepared to have your nose rubbed in some pretty tough realities. It breaks one of the most basic rules of "feel good" movies (which I am Legend manifestly is not): The dog dies. And, yes, that part is hard to take. But she doesn't die in vain. It hurts, but it is a pain worth having. Just don't say you weren't warned!