[...] the Republic is better read as a critique of the status quo than as a straightforward policy proposal. The fundamental claim is that collective well-being depends on the readiness of individuals to act for the common good. Nowadays we tend to see such actions in a moralistic frame that pitches saintly altruism against tawdry egoism, but for the pre-Christian Greeks altruism in the sense of impartiality between one’s own well-being and that of others was pretty much unthinkable: loosely stated, the main thesis of the Republic is that working for the common good is necessary for your own happiness. There are some contexts where it seems totally natural to consider your own well-being as bound up with that of others. Parenting seems like a prime example: when you change a diaper, you’re clearly acting for the sake of someone other than yourself, and so not being egoistic, but at the same time you’re not exactly being altruistic—the fact that it’s your own child means that you have those phantom-limb experiences where another being’s pleasures and pains become your own, so there’s a sense in which you’re relieving your own discomfort. Such expansion of the self can also occur between members of a team: esprit de corps literally means having the spirit of one body. If that spirit could be extended to the whole community, Plato thought, we could speak of a genuine body politic. Many have questioned whether it is possible to extend the notion of “one’s own” that far, but it seems obvious that patriotic feeling has sometimes led to acts of non-altruistic self-sacrifice. Whether such patriotism can be maintained in the absence of existential emergencies or local rivalries is another matter, but for Plato the more important question is whether it can be maintained in the presence of private family ties.