*Probability theory is nothing but common sense reduced to calculation* — Pierre-Simon Laplace 1749-1827)

So when you hear *we can't forecast the future*, or *estimates are evil*, or *we can't know what we need to do until we start doing*, focus on the last part of the quote — if you don't apply probability theory and its partner statistics, they are correct and missing that basic *common sense. *If we apply basic statistically thinking to project management issues, we can calculate the probability of anything. The resulting probability may not have sufficient confidence levels - but we can calculate non the less.

When you hear *we can make decisions without estimating the cost, schedule, or capability impacts of those decisions*, consider Laplace and the *nonsense* of that notion. And a recent example of how to *do the math* for forecast the future behaviour of a project in a specific domain *Earned Value Meets Big Data *and the annotated briefing of the same paper.