I should first clarify whose position is being discussed: The Welfare Footprint Framework itself does not prescribe a particular theory of sentience or affective capacity. It treats positive and negative affective experiences as the core of welfare, but it remains open about the precise biological mechanisms that produce them and about how affective capacities should ultimately be compared across species. The ideas in this series of posts are therefore better understood as our provisional contribution to this problem, developed largely for the practical purpose of making interspecific Welfare Footprint comparisons possible. They should not be presented as an official WFF position on whether sentience is categorical or graded.
My own personal view is that the biological capacities associated with sentience can vary continuously, while the minimal presence of affective experience is categorical. Nociception, memory, learning, integration and considerable information-processing capacities may all have existed in pre-sentient ancestors. My hypothesis is that, at some point, affective states became part of the control system, providing a common currency through which signals and memories could be valued and used to guide behaviour. Under this view, there is a difference between a system in which something can feel good or bad and one in which nothing does, even though the capacities supporting that transition and the affective capacities that follow it are graded.
An analogy would be an exoplanet candidate. Astronomers may have evidence of varying strength that a planet exists around a distant star. Their confidence may be 20%, 70% or 99%, but the planet itself either exists or does not. Graded evidence does not require the underlying fact to be graded.
Likewise, the fact that behavioural, neural and physiological evidence exists on continua does not by itself imply that sentience must exist on a continuum. It means that our confidence about its presence is graded. This not requires assuming a simple or already known boundary in the evidential space. The biological transition may be complex, and we may be deeply uncertain about where it lies.
In your hypothetical, if we had both complete physical evidence and an adequate biological account of which forms of organization generate affective states, then yes: under my working view, the answer for a particular organism at a particular time would be either that affective experience was present or that it was absent. Our proposed classifications reflect our incomplete evidence and incomplete biological understanding, not a claim that the organism is partially sentient in proportion to our confidence.
This is also why the tool uses a sentience-plausibility gate followed by a separate affective-capacity analysis. The first asks whether there is sufficient reason to infer that anything can feel good or bad for the organism. The second asks, conditional on that, how differentiated and intense those states could be. The first is treated categorically in the underlying hypothesis but uncertain in our knowledge; the second is explicitly graded.
Thanks, Vasco. I think our respective positions are now becoming quite clear, and we may be reaching the point where further progress depends more on scientific and theoretical work than on extending the analogies.
My exoplanet example was intended only to distinguish graded evidence from the underlying fact being investigated. Whether a candidate celestial body exists is different from whether an already known body satisfies one of several proposed definitions of a planet. Margot’s figure addresses the latter question. My analogy concerned the former.
As I noted above, my position is that the biological capacities supporting sentience (and our evidence about them) can vary continuously even if the minimal presence of affective experience is categorical. What I would add here is that gradual evolution does not make such a transition implausible. Existing structures and capacities can be co-opted into a new functional role, as captured by the concept of exaptation: a feature that originally evolved for one function, or for no particular function, may later acquire another. This may make the evolutionary onset of sentience especially difficult to locate, because there need not be an obvious biological marker separating the earliest sentient organisms from their closest non-sentient relatives. The transition may have depended on a very small biological change, or even on a change in context that allowed existing mechanisms to perform a new role.
So yes: under my hypothesis, two organisms could in principle be extremely similar while affective experience was present in one and absent in the other. I do not find that paradoxical. A small difference in a complex system can sometimes make a new causal process possible. The supporting architecture may vary continuously even though the process we are asking about either occurs or does not occur in a particular organism at a particular time.
Your concern about one organism receiving some moral value while the other receives exactly none introduces a separate normative question. That conclusion does not follow automatically from the claim that sentience is categorical. The sentience gate in the tool is not intended to assign moral worth. Its focus is narrower—and appropriately so, given that it concerns one of the biggest mysteries in science: it asks whether affective states, and therefore sentience in the relevant sense, plausibly occur in the target taxon.
Turning to the normative question, assuming that every organism has more than exactly zero moral value is a possible normative position, but it is not a scientific consequence of treating biological capacities as continuous. It would require its own justification.
Speaking only for myself—and separately from the analytical commitments of the Welfare Footprint Framework—my principal concern is severe suffering, particularly Disabling and Excruciating Pain. Annoying and Hurtful experiences remain genuine components of welfare and should be recorded in WFF analyses. But the presence of lower-intensity negative affect alone would not ordinarily make an organism or intervention a leading priority for me, especially given the scale of severe suffering that already exists and the need to consider where effective intervention is possible.
This is one reason the affective-ceiling question matters so much to me. Nature is not benign, and neither are most modern animal-production systems. Given the scale of severe suffering that already exists, I think our attention should be concentrated where the most intense suffering is possible. If biologically simpler sentient organisms have narrow affective ranges and cannot experience severe Pain, I would find that reassuring.
I therefore think our remaining disagreement concerns at least two distinct questions. Scientifically, you favor treating sentience itself as graded, whereas I regard its minimal presence as categorical while treating our evidence—and subsequent affective range, resolution, and intensity—as graded. Normatively, you favor assigning every organism more than zero moral value, whereas my own priorities are concentrated on organisms capable of severe suffering, particularly where meaningful intervention is possible.