Editorial overview: Consciousness on the borders of life and death

Our ability to adequately define life and death and other states in between has resulted in many controversies philosophically and empirically, with arguments supporting or detracting from issues such as the harvesting of organs for transplantation, the right to life, sentience, consciousness during fetal development, altered states of consciousness, locked-in syndrome, and life itself. According to a generally accepted view, life can be described as a quality that differentiates entities possessing physiological activities such as self-sustenance, growth, communication, and replication from those that do not. Entities that have concluded (expired) or those that never possessed such functions, we classify as nonliving or inanimate. Biology is the science concerned with the study of life. Unfortunately, there exists no consensus regarding life's definition. This is partly because life is a progression complicated by a lack of a complete understanding of the characteristics of living things. Death is the permanent termination of all biological processes sustaining an organism, and as such, it is the end of its life, offering a boundary to life. However, mental life and consciousness may end earlier than the moment at which all biological processes cease. This themed issue provides multidisciplinary perspectives for a better understanding of life, death, living behavior, adaptive function, and consciousness-supporting behavior of organisms. This special issue includes 19 reviews, both on theoretical work and experimental findings, that address the development of consciousness from fetus to the changes occurring throughout life, up to the very edge of death, in both humans and nonhumans. Mudrik and colleagues [1] review different theories of consciousness and examine the conditions under which conscious experience contributes to a life being considered worth living, highlighting the ethical implications of consciousness across species and states. On the other hand, Buchman [2] describes a new framework for categorizing life along its measurable continuum, with the aim of harmonizing our normative perspectives with the rapid advancements in medical innovation.