 Recent scholarship has defended the traditional ideal of vera causa both as a normatively adequate methodological standard for experimental biology as well as a standard that biologists are actually committed to. The ideal requires that scientific explanations of a phenomenon cite true causes or verae causae. To qualify as a true cause, an entity must satisfy the following criteria (e.g., Hodge 1992): First, it must have been shown to exist. Second, it must be causally competent to produce the phenomenon in question. Third, it must be causally responsible for this phenomenon. Importantly, the evidence for existence must be independent from the evidence for causal competence. Thus, the mere fact that an entity’s purported causal capacities are able to explain a phenomenon dies not alone constitute sufficient evidence for its existence. What this means, obviously, is that an inference to the best explanation (IBE) of a phenomenon cannot alone justify acceptance of a postulated entity. It must always be accompanied by independent evidence for existence.