Firstly, you are correct that 'all x are Y' statements escape my critique, so if U were to claim a more modest and precise F[1, "all (human?) motives are selfish", then there would be a different argument to be had.
At this point I'd like to revisit our old friend, F = everything is selfish. Truth be told, my guess is that a hypothetical is involved here - the person, call faer U, who claims F imagines in faer mind what selflesness is and going by faer belief in F, this imagined selflessness precludes any and all benefit to the selfless person. In other words, there's a "...background...", the imagined selflessness U has in faer mind. — TheMadFool
I hesitate to characterise the mind of U - for about 3 seconds, before concluding that the the asshole deserves every insult I am about to lay on them. By U's own hypothesis, their motive for claiming F or F1 is selfish. They cannot dispute that. Nevertheless, they must
be able to imagine selflessness in some form, or have some experience of it, simply for 'selfish' to mean something (as per original argument). So I will assume that U considers that raindrops fall, when they do, selflessly, and that in general, things that have no awareness have no self. That is U's claim is F1.
Statements of this nature can be either observational or definitive.
An F1 observational justification would be along the lines of - J1. "I've heard a lot of claims of unselfish motivation, and every time I challenge them, they turn out to have been selfish after all."
Whereas the definitive justification would be a priori - J2. "If it isn't selfish, it doesn't count as a motive."
Thus if a philosopher "knows" that all swans are white
, he can preserve his claim in the face of those Australian birds, simply by insisting that they are black long necked ducks. They cannot
be swans, because a swan is a white bird with a long neck. Such philosophers are best ignored.
So I address myself to J2.
K mows his neighbour's lawn. K claims he did it not for himself, but for his neighbour. U suggests various other motives.
1. K wants to stop weeds spreading to his own patch, or an untidy garden lowering the tone.
2. K expects his neighbour to return the favour in some way.
3. K wants to encourage a neighbourly ethos that will benefit him in the long run.
4. K expects some kudos and respect.
5. K wants to feel superior.
6. K wants to feel
This is how it generally goes; U looks first for immediate benefits, then for reciprocal benefits, then for indirect and social benefits, and in the last resort for psychological benefits. And any of these can be motives, and often are.
Except 6. K is not an idiot. K knows that wanting to act so as to feel or be unselfish is selfish. So it does not function as a motive unless it is an unconscious motive. And now U needs some justification for imputing this unconscious motive to K, and indeed to every act by everyone ever. Such misanthropy starts to look more like an excuse for being selfish oneself, more than a coherent psychological or moral theory.