"Doubt is not a pleasant condition, but certainty is absurd." -- Voltaire (François-Marie Arouet)
My friend Jackie asked me today to explain why I said that I was 99.999% certain there was no God, but not 100% certain. I told her that, as a good scientist, I don't think that we can ever be 100% certain about anything, to which she replied that this doesn't make sense. I sympathise with the fact that she didn't quite understand what I was saying. I think this is a counter intuitive concept for many people and I often see students confused by this idea. Therefore, I thought that I would provide an explanation here as to why I don't think we can ever be 100% certain about almost anything.