Excusable ignorance not only undermines moral culpability but also agent-responsibility. Therefore, excusable ignorance absolves of liability for costs. Specifically, it defeats liability that is meant to be derived from causal responsibility wherever strict liability cannot be justified. To establish these claims this paper assesses the potential of arguments for liability of excusably ignorant agents and thereby demarcates the proper domain of strict liability and traces the intuition that seemingly supports strict liability accounts to more general principles. The paper concludes that (...) liability cannot be justified in cases of excusable ignorance. Finally, it stresses that although excusable ignorance defeats the link from causal responsibility to liability for costs this does not imply that victims are left to fend for themselves. (shrink)