There's really two components to ID:
* A No-Go Theorem (http://en.wikipedia.org/wiki/No-go_theorem) on the likelihood of spontaneously arising life, or of it reaching some threshold in evolutionary development naturally.
* ...which leads to "the design inference", which posits that the characteristic of intelligence is able to overcome the problem established by the no-go: that life exist, but could not allegedly have arisen from a random process.
Now certain no-go theorems claim something is physically impossible, like transmitting information faster than the speed of light, some are about the provability in mathematics like Godel Incompleteness theorem, but the ID no-go theorem is about being statistically imprlausible- but what is implausible in a Big, Old Universe? Something like 1/Number of atoms in the universe is sufficiently low (2^82), and you can demonstrate this easily by thinking of DNA code 1/4^N where N = min num of base pairs for self-replication, where N~100,000 M genitalium. This is a very naive model, but it's a start: see <PERSON> work for better maths: http://www.youtube.com/watch?v=RlYS_GiAnK8
The design inference is really <PERSON> domain, and I'll refer you to him, this is much more a philosophic argument. One thing that's important to note for people who are dismissive of ID is that this is about reasoning about intelligence in the abstract, not the manifestation in physical form, not "some being".
What's my opinion? Could I get back to you in 300 years? We'll finally have data on thousands of other planets and whether any of them have ever harbored life, and that I think would be the falsification of ID if other life was found. 855
But I think both a barren universe, and one with other life are both plausible given what we know now. That's why I don't get why people are so staunch on this issue: it's impossible to know the one key thing we need to know in this debate in our lifetime. But in a few generations we in fact will have this answer. We get to live in some interesting times. 283