<p>How should we assess systems whose mnemonic status is contested? There are, for instance, debates over whether immune memory is “really” memory, or akin to memory as ordinarily attributed to human cognition. In this paper, I challenge two arguments often given by detractors in this debate. The first is that the system does not exhibit errors exemplified in human memory. The second is that it can be described and explained in causal terms alone. I argue that our limited knowledge of the causal basis of immunological phenomena and human memory undercuts our ability to conclude that one is merely causal while the other is not. By consequence, it is unclear why we should reject that the immune system exhibits these errors. With my challenges, I question whether we are consistent in assessing alleged mnemonic systems. Though we have schematic causal accounts of both systems, we have differing expectations of what we can conclude about them. Yet, it is unclear what might warrant appeals to these expectations.</p>