 Comparative process tracing would be futile if, in order to know that C causes E in the target species or population, we would have to compare all the stages of the process between model and target. This is because in order to do so, we would have to know all stages of the process through which C causes E, but if we did, we would already know that C causes E. This brings us back to the extrapolator’s circle. Steel now argues that comparative process tracing avoids the extrapolator’s circle by demanding processes to be compared only at stages where they are likely to differ and assuming that differences between model and target matter only to stages that are downstream from where they obtain. Thus, if we compare an intermediate stage of the process which obtains in the model with that stage in the target and find them to be relevantly similar, then the only differences that may still obtain will be downstream from this stage. We therefore do not require knowledge of the entire process from C to E in the target, and the extrapolator’s circle is successfully avoided.