Symmetry
The assumption that no being's interests matter more than another's merely as a matter of fact.
What it commits you to
Symmetry is the working assumption behind the golden rule, Singer's equality, and Rawls's veil. It is not a metaphysical thesis but a refusal to accept that any being's interests count for more without a reason that could be defended to that being. Its practical use is as a diagnostic: ask whether any moral weight has been smuggled in on the basis of something arbitrary.
Which realms lean on this
Philosophy carries the arguments the other four kinds are downstream of — what an agent is, what a person owes, what a rule is for.
philosophy · 8 realms — The Care Weft, The Contractual Court, The Existential Wilds, The Kantian Citadel, The Longview Foundry, The Middle Kingdom, The Pragmatic Wharf, The Sangha Terraces.
See also
Veil of ignorance
philosophyA device for choosing principles without knowing which position in society you will occupy.
Speciesism
ethicsTreating an entity's species membership as the reason for its moral consideration.
Golden rule
philosophyDo to others only what you would have done to yourself.
Capabilities approach
ethicsDevelopment is judged by what people are actually able to do and be, not by income.