Every once in a while I experience a feeling of foreboding, as if something's soon going to happen that I won't like one iota. Sometimes I know what's to come, but most of the time it's just a sort of itching sense under the skin that you can't quite shake off. Don't look at me like I'm a lunatic; this is the human "sixth sense", or part of it, and I'm certainly far from being alone in feeling a little off kilter now and then.