Three perspectives

The first cluster of substance papers addresses the foundations and meanings of sentience. Karim Akerma questions the common assumption that pain was the first evolutionary sensation, suggesting instead that primitive consciousness may have begun with neutral or even pleasant experiences. If this is right, then suffering is not the inevitable guardian of life but a later development, and our arguments about the evolutionary role of sentience must be reconsidered. David Benatar argues that in the actual world, sentience is both necessary and sufficient for moral standing, grounding ethical concern in the capacity to have sentient interests. His distinction between functional, biotic, sentient, sapient, and self-conscious interests provides a structured way to determine moral relevance, even as it leaves open difficult questions about how competing interests should be weighed. Julio Cabrera challenges the reliance on non-sentience in abortion ethics, showing that the moral permissibility of abortion can be defended on other grounds. His five arguments—from the formal paradox argument to the manipulation argument—suggest that the moral debate cannot be settled simply by pointing to the absence of foetal sentience. Thana Campos develops a personalist conception of suffering, situating it not merely in subjective experience but within communal practices of meaning-making and shared flourishing. On this account, suffering becomes an ethical challenge that calls for a collective response, grounded in love, justice, and relational responsibility.

A second group of contributions turns to applied and emerging contexts where the possibility of sentience is particularly contested. Søren Holm and Jonathan Lewis examine whether neural organoids might develop sentience, critically assessing analogies with known organisms, inferences from neural function, and panpsychist commitments. They conclude that current organoids fall short of sentient thresholds but offer a principled framework for when precautionary restrictions might be warranted in the future. Oscar Horta and Iria Murado-Carballo argue that wild animal welfare deserves recognition within the One Health paradigm, reframing interventions not only as matters of human and ecological benefit but also of sentient wellbeing. Their paper illustrates how existing programs, from vaccination campaigns to parasite control, could be broadened to include concern for animals themselves, and how cross-disciplinary research can make such interventions more effective. David Lawrence proposes a spectrum-based model of moral status, structured around thresholds of sentience, consciousness, and sapience, to move beyond the entrenched binary of persons and things. By conceptualising moral status as a gradient, his framework offers a flexible tool for governance in areas where current law provides inadequate guidance, such as embryo models and brain organoid research. Jonathan Leighton advances an ethical framework that prioritises the prevention of extreme suffering across species and substrates. He argues that intense suffering has an inherent urgency that demands action and introduces novel metrics such as Years Lived with Severe Suffering (YLSS) and Days Lived with Extreme Suffering (DLES) to track what matters most.

The third set of papers engages with antinatalist perspectives and the paradoxes of sentient existence. Masahiro Morioka analyses sentiocentric antinatalism as an unsolvable paradox: the attempt to prevent all births of sentient beings would itself impose obligations on antinatalists to survive in order to fulfil their mission. Drawing parallels with the paradoxes of time travel, Morioka shows how philosophical puzzles can illuminate the ethical tensions at the heart of antinatalism. Amanda Sukenick traces recent debates within antinatalist thought, distinguishing anthropocentric forms that seek voluntary human extinction from sentiocentric forms that call for the eradication of all sentient life. Her analysis situates these positions within both academic philosophy and online movements, mapping the diverse motivations and controversies that shape contemporary antinatalist discourse. Konrad Szocik emphasises the inescapable suffering inherent in sentient life, urging bioethics to take antinatalist intuitions more seriously. He argues that pronatalist ethics, by celebrating life without regard for its inevitable costs, magnifies preventable suffering and neglects the moral weight of sentience. Matti Häyry returns to the roots of contemporary antinatalism in David Benatar’s Better Never to Have Been, clarifying the scope and limits of its application to human and non-human life. He argues that while Benatar’s bipolar pessimism grounds a coherent case for human antinatalism, its extension to all sentient beings introduces conceptual ambiguities that must be acknowledged.

Taken together, these contributions map the contours of current thinking on sentience, from its evolutionary beginnings and philosophical justifications to its implications for emerging biotechnologies, animal welfare, and debates on the value of existence itself. They show that sentience is neither a marginal nor a settled concept but a central and dynamic category in ethical reflection—one that compels us to reconsider how we value life, address suffering, and imagine our responsibilities across species and technologies. By exploring its foundations, testing its applications, and confronting its paradoxes, this issue offers a multifaceted contribution to the ongoing debate: whither sentience?

A motivational case with a tentative practical solution: C. elegans

The immediate impetus for this special issue comes from the BaBots project (https://babots.eu/), a European research initiative in which populations of Caenorhabditis elegans are modified to perform simple tasks. At first glance, ethical oversight of such work appears straightforward: the organisms are minuscule roundworms without autonomy or self-awareness, and traditional frameworks of research ethics—concerned with harm, safety, and consent—seem to absolve the project of controversy. Yet questions arise once the lens of sentience is applied. Contemporary science has shown that C. elegans may satisfy several criteria of sentience, including nociception and analgesia preference, even while failing to meet others, such as sensory integration. Whether these findings amount to “substantial evidence” of sentience or fall short of the threshold remains contested, leaving the ethical status of these organisms unsettled.

Here the articles in this special issue help to illuminate our predicament. The contributions on the foundations of sentience complicate the assumption that pain is the primordial or necessary hallmark of consciousness. Akerma’s suggestion that early consciousness may have been neutral or even pleasant, and Benatar’s claim that sentience is sufficient for moral standing, both sharpen the stakes: if C. elegans were capable of even rudimentary feeling, then their treatment could matter morally. Cabrera’s reflections on abortion ethics remind us that non-sentience cannot be the only criterion in moral debates, while Campos’ emphasis on communal meaning-making expands the discussion of suffering beyond private experience to shared ethical responsibility.

The applied perspectives also bear directly on BaBots. Holm and Lewis’ careful parsing of possible organoid sentience provides a template for thinking about uncertain or borderline cases. Their insistence that regulation should follow only once there is a non-trivial likelihood of valenced experience suggests that, at present, C. elegans modifications may not demand radical constraints—but that vigilance is warranted. Horta and Murado-Carballo’s advocacy for wild animal welfare underlines the moral pull of suffering in nonhuman populations, inviting us to take seriously the welfare of sentient individuals even when broader ecological or human-centered rationales dominate. Lawrence’s spectrum model of moral status offers a way to position C. elegans between “mere things” and full moral persons, while Leighton’s urgent call to prioritise extreme suffering directs attention to whether modified worms might ever endure such experiences.

Finally, the antinatalist discussions resonate with the BaBots case by questioning whether sentience itself is a good worth preserving. Morioka’s and Sukenick’s analyses of sentiocentric antinatalism highlight the paradoxical obligation to prevent or end sentient life altogether; Szocik’s emphasis on suffering as the inescapable consequence of sentience reinforces this concern. Häyry’s critical return to Benatar’s “bipolar pessimism” shows how far these views can be extended, while also noting the conceptual limits of applying them wholesale to all forms of life. For BaBots, these perspectives do not dictate immediate cessation but remind us of the deeper ethical tensions underlying the creation and use of sentient organisms.

Taken together, the special issue points toward a tentative practical resolution. The balance of current scientific evidence suggests that C. elegans, even in modified forms, are unlikely to be sentient in any morally demanding sense. Yet the philosophical arguments gathered here caution against dismissing the possibility outright. A prudent stance combines precaution—continuing to monitor developments, remaining alert to signs of subjective experience—with further study, both empirical and conceptual. Meanwhile, symbolic attitudes of respect for life and sensitivity to suffering can guide the ethos of the project, ensuring that even low-probability harms are not trivialised. The practical conclusion may therefore be summed up as: no decisive reason to halt the work, but ample reason to remain attentive, reflective, and ready to recalibrate should new evidence or arguments emerge.

Sentience reconsidered

This special issue has traced the many ways in which sentience shapes our ethical landscape: as a criterion of moral standing, as a marker of suffering and flourishing, as a challenge for emerging biotechnologies, and as a source of existential puzzles about the value of life itself. The BaBots project exemplifies how these theoretical debates become practically urgent, demanding careful reflection even in cases where the evidence for sentience is uncertain or contested.

The lesson running through the contributions is neither alarmist nor complacent. Sentience is revealed as a concept at once fragile and weighty: fragile, because its boundaries shift under scientific scrutiny; weighty, because wherever it is found, it transforms our ethical responsibilities. For now, the wisest course may be to proceed with caution, with humility before the unknown, and with openness to further inquiry. In this spirit, the present volume invites ongoing conversation about what sentience is, where it matters, and how it should guide the ethics of research, policy, and life itself.