 An alternative general framework, proposed by Faith (1994), avoids weaknesses of the objects-differences strategy. The framework side-steps the idea of differences and instead uses the inferred relative number of biodiversity “units” among any given set of “objects”. If “biodiversity” is variation or variety in the sense of units (such as species) that we ideally count-up, then what are those units or elements that make-up biodiversity? The units of interest logically cover more than just the species level (and even the core idea of “species” may consider alternative classifications, such as those in folk cultures; Oksanen 2004). Maclaurin and Sterelny’s argument (2008: 154) that option value “links variation and value” considered option value for units across all levels of biodiversity.