This Michael Leunig cartoon wafted its way from Australia the other day. My reaction was: doesn't this satirise affluent developed-economy lifestyles, especially those enjoyed by my generation, rather than the idea (or, for some, ideal) of sustainability?
On being provoked to think again, this is another view, ...
Up to now, I suppose, the someone else in question whose cake is being consumed (though not by the two philosophers in the picture, by the look of it) is that of the current and future poor. However, if resources are actually at last running out, and if the biosphere is as badly placed as we're told it is, then it could be everyone's future cake that's being gobbled up.
But "sustainability" is supposed to help prevent this, whether by sharing cake more equitably (the socialist vision), baking more cake (the capitalist version), or by doing without cake in the first place – banning it, more like (the let's go back to the golden age, aka miserablist view).
There are, of course lots of folk who think that they are being sustainable because they've been on all those ESD1 courses and are doing what they're told: driving more carefully, walking to the shops, recycling, composting, wearing thicker sweaters, drinking fair trade whisky (I've made that up), etc., etc.
But they would never say what the cartoon blokes say because they're not all that self-aware. Neither are they usually cynical. They really believe they've cutting down on other people's cake.
I suppose I am having trouble identifying who the cartoon characters are.