Hi,
He'll need 2 major things before being able to be trained. First, he need to recognize the need to go and know that he is going. You can test this by letting him run around the house without pants or a diaper on and watching his expression when he goes (it'll make a mess but at least you'll know). If he stops and looks and seems interested in what he is doing he may be ready, if he continues on with whatever he was doing in the first place he's probably not. Also, he needs to be able to get to the bathroom, take down his pants and go. There will be times when you can't make it to the bathroom with him in time and you don't want him to have an accident just because you couldn't get him there in time.
Most kids are trained by 3 they say boys by 4. My daughter was also very bright, talking at 7 months (full on sentences by a year), walking at 9 months and reading at 3 but she wasn't fully trained (night and day) until 2.5. My son is another story all together. He just doesn't get it yet so I'm waiting to train him (he's 2). Good luck, and the most important thing is not to get frustrated. If he doesn't get it right away or seems to not like it. Try again in a few months!
Krissey