This paper examines the problem of distilling conflicting interpersonal comparisons into a single set of interpersonal comparisons. The mapping that achieves this has a richer co-domain than all social choice problems (and a richer domain than most social choice problems). The set of mappings satisfying a mild set of restrictions is very small. If interpersonal comparisons embody ratio-scale comparability then the mapping is Cobb-Doublas in form; if interpersonal comparisons embody no more than level and difference comparability then the mapping must be dictatorial and it is impossible to combine different interpersonal comparions. The restuls can be applied to the problem of aggregating subjective probabilities.