Carl Sagan, one of the great systems thinkers of all time, said "In order to bake a cake from scratch, you have to invent the universe".  Allan Savory has said, in effect, that, in order to evaluate your proposed use of biochar, you need to explain how you wish your life to be.  Biochar, like any other agricultural tool, cannot be fully appreciated outside of specific contexts. The presentation doesn't exactly invent the universe, but for the first time anywhere, it applies the fundamental principles of Holistic Management to the design, evaluation and execution of specific biochar systems in their specific contexts.  In doing so, it provides a guide for evaluating any proposed biochar system in its own specific context.   It draws on  four specific examples - 1 acre and smaller fields trials in a Mediterranean climate, a montane homestead scale smallholder ranch, broad fields/shortgrass prairie grazing  and a half million acre tropical forest restoration - in addition to insights from several other projects.  It provides an introduction and specific guide to the methodology that can be used in any context to evaluate and design the best and most effective use of biochar, including the most effective production, preparation and application regimes for a particular context.  The method sometimes has some surprising results: of the four prime examples analyzed, few if any can guess which of the four main  contexts discussed presents a compelling case for (or against) us of biochar.  The wisdom to know the difference may be the most powerful biochar tool of all.