 The grammatical logic of it eludes me. It should mean, I am telling you the following for a good reason. But check out that but. Can we ascertain its function in the phrase? Now, perhaps others have already examined this matter, but I tend to ignore others, for if hell is other people and ignorance is bliss, it stands to reason that the road away from hell is paved with circumventions, so as a rule I pass. But in the course of the day, one can't help but notice people saying things like, not for nothing, but...