You raised a good point. Yes, I guess I agree that when there is only a positive experience and no negative, the welfare is definitely positive, even if the positive experience is very small. But thinks get tricky when there are both positive and negative experiences, as is the case for almost all sentient beings, and probably also for nematodes if they are sentient. The more welfare is composed of positive and negative parts, the more difficult it becomes to compare it with a zero welfare level. Might have to do with information processing capacity. Adding up many positives and negatives is more difficult that considering a single positive or negative value. Evaluating mixed experiences (with both positive and negative parts) might require a more coarse-grained approach. The level of coarse-graining might relate to the neutral range: the more coarse-graining is used, the wider the neutral range.
You raised a good point. Yes, I guess I agree that when there is only a positive experience and no negative, the welfare is definitely positive, even if the positive experience is very small. But thinks get tricky when there are both positive and negative experiences, as is the case for almost all sentient beings, and probably also for nematodes if they are sentient. The more welfare is composed of positive and negative parts, the more difficult it becomes to compare it with a zero welfare level. Might have to do with information processing capacity. Adding up many positives and negatives is more difficult that considering a single positive or negative value. Evaluating mixed experiences (with both positive and negative parts) might require a more coarse-grained approach. The level of coarse-graining might relate to the neutral range: the more coarse-graining is used, the wider the neutral range.