Yoshiyuki Hayashi

This article proposes a methodological schema for engaging in a productive discussion of ethical issues regarding human brain organoids, which are three-dimensional cortical neural tissues created using human pluripotent stem cells. Although moral consideration of HBOs significantly involves the possibility that they have consciousness, there is no widely accepted procedure to determine whether HBOs are conscious. Given that this is the case, it has been argued that we should adopt a precautionary principle about consciousness according to which, if we are not certain whether HBOs have consciousness—and where treating HBOs as not having consciousness may cause harm to them—we should proceed as if they do have consciousness. This article emphasizes a methodological advantage of adopting the precautionary principle: it enables us to sidestep the question of whether HBOs have consciousness and, instead, directly address the question of what kinds of conscious experiences HBOs can have, where the what-kind-question is more tractable than the whether-question. By addressing the what-kind-question, we will be able to examine how much moral consideration HBOs deserve. With this in mind, this article confronts the what-kind-question with the assistance of experimental studies of consciousness and suggests an ethical framework which supports restricting the creation and use of HBOs in bioscience.