Much discussion of Moral Circle Expansion seems hampered by lack of conceptual clarity about what the Moral Circle means.
There are a lot of distinctions that need to be drawn, but here are two positions on one dimension:
The moral circle merely refers to which (groups or types of) entities are viewed as possible targets of moral regard
The moral circle refers to the amount of actual moral concern granted to such entities
A lot more distinctions should be drawn on this dimension alone (e.g. for “actual moral concern” are we interested in abstract attitudes of concern, actual amount of effort extended, or actual treatment extended), but even these suffice for now.
On the first view, which seems somewhat closer to original uses of the term, it does seem like retrenchment of the Moral Circle should be expected to be quite rare, at least once you reach contexts like our own (in WEIRD societies) where there are extremely prevalent memes about at least potentially considering entities as possible moral targets if they might be persons in any sense (or more generally in contexts where the conditions for considering the possibility of including some group in the moral circle are as extensive and plural as they are now). It seems relatively hard for groups to fall entirely out of the moral circle in the first sense, in such cases, except in cases like those you mention where we decide that certain entities don’t exist or aren’t sentient.
With the more expansive second sense of Moral Circle (which seems to be what people are using), where all that is required for Moral Circle expansion/retraction is an increase or reduction in moral concern extended (as seems to be implied by examples such as more/less care being granted to the elderly and so on), it seems like the Moral Circle should be expected to be expanding and retracting near constantly on an individual or group basis. This is especially so if we understand degree of moral concern as meaning the actual extend to which needs are weighted and help extended (in which case this will, almost necessarily, be pervaded by tradeoffs in a near zero sum fashion) which is why further distinction being drawn within this category is so important.
Much discussion of Moral Circle Expansion seems hampered by lack of conceptual clarity about what the Moral Circle means.
There are a lot of distinctions that need to be drawn, but here are two positions on one dimension:
The moral circle merely refers to which (groups or types of) entities are viewed as possible targets of moral regard
The moral circle refers to the amount of actual moral concern granted to such entities
A lot more distinctions should be drawn on this dimension alone (e.g. for “actual moral concern” are we interested in abstract attitudes of concern, actual amount of effort extended, or actual treatment extended), but even these suffice for now.
On the first view, which seems somewhat closer to original uses of the term, it does seem like retrenchment of the Moral Circle should be expected to be quite rare, at least once you reach contexts like our own (in WEIRD societies) where there are extremely prevalent memes about at least potentially considering entities as possible moral targets if they might be persons in any sense (or more generally in contexts where the conditions for considering the possibility of including some group in the moral circle are as extensive and plural as they are now). It seems relatively hard for groups to fall entirely out of the moral circle in the first sense, in such cases, except in cases like those you mention where we decide that certain entities don’t exist or aren’t sentient.
With the more expansive second sense of Moral Circle (which seems to be what people are using), where all that is required for Moral Circle expansion/retraction is an increase or reduction in moral concern extended (as seems to be implied by examples such as more/less care being granted to the elderly and so on), it seems like the Moral Circle should be expected to be expanding and retracting near constantly on an individual or group basis. This is especially so if we understand degree of moral concern as meaning the actual extend to which needs are weighted and help extended (in which case this will, almost necessarily, be pervaded by tradeoffs in a near zero sum fashion) which is why further distinction being drawn within this category is so important.