There is a reason why we promise to tell the truth, the whole truth, and nothing but the truth. Each of these is a distinct thing. It’s hard to ignore the concept of Truth, especially in an election year. Accusations of lies, assertions of truth, fact checking, and apologies for “miss-speaking” seem to be everywhere. Philosophers have struggled with the concept of truth for millennia, yet it is still one of those concepts that we seem to understand intrinsically until we try to define it. So what do we really know about the truth in data, and how do we know we know it? The first thing that becomes obvious in a Big Data world is that finding the truth can be a matter of definition and perspective. Determining which data is true or accurate when there is no reference to compare is one of the fundamental problems in computer science.