I have never found Sartre’s argument about how in choosing for oneself one chooses for all mankind to be convincing. His point seems to be that we can’t help but make for ourselves the choice we consider “best” (assuming we’re acting “de bonne foi”, that is, that it’s a deliberate choice following the principles of existentialism) and that we automatically consider that what is best for us is best for everyone. Hence, in choosing what we think is best for us, we are automatically assuming it’s best for all people and hence that we are “shaping a vision of mankind” by each choice we make.
I’ve always found flaws in that assertion. First, but perhaps least provable, the assumption that we always choose what we consider “best”-I think the only way this is strictly true is if we define “best” to be “that which we choose.” Otherwise, speaking from experience, I can certainly make choices that are not “best” in any (at least) objective sense. But neither do I think they’re automatically “de mauvaise foi.”
Another problem: while there are obviously many ways in which I’m a “typical person,” there are (equally obviously to me, at least) many ways in which I’m not. Hence, I don’t think that what is “best” for me in every situation is automatically what’s best for others. Hence, when shaping my own character/self, I am not necessarily implicitly shaping “all of humanity’s.”
Although, as I sit here thinking of specific examples of this, they may be “local issues” rather than global ones, so maybe if one makes the choices under consideration fundamental enough (whether to hurt others deliberately or not, for instance), my objection might be mitigated. But in that last specific example, for instance, even though I have occasionally decided to hurt someone else deliberately when I had been badly hurt myself, I don’t think that’s a choice I “should” have made and hence it’s not a choice I think others “should” make in similar circumstances. I guess I need to read more of Sartre’s non-fiction and see if he ever delves into those sorts of questions in any detail.
(I know what you’re thinking: “When is he going to delve?” LOL)
A third problem: How in the world do we know what’s “best”? Sometimes, choices are made in relative ignorance and we’re aware that it’s so. Again, unless you’re going to get very reductionistic and simply define “best” as “the choice that’s made”, I think it’s difficult to argue that even deliberate choices are always for the best. Maybe Sartre feels it’s implicit that “best” means “best we can think of at the time even being aware that in principle there are probably better ones.”
However, near the end of the extended essay, Sartre again makes this argument (that in choosing what’s best for us, we inevitably choose what’s best for everyone), this time in a context that I find much more convincing. This time around, he posits that because people are inherently social animals we cannot in any meaningful sense as human beings live totally alone. Thus, since we are inherently social, we cannot help but shape our character/sense-of-self in response to the judgments (though he doesn’t use that very Clamencian word) of those around us. In which case, it follows that our judgments also have some effect on the way they shape their characters. In which case, it becomes more plausible (I think) to assert that in making choices for ourselves, we are simultaneously choosing “for all mankind.” Not totally convincing, mind you: I still think there are people/occasions where a decision is made locally that the decider does not feel is globally “best.” But at least this decisions-have-social-implications perspective seems to me to have some basis other than thin air ;-).
(And yes, it really is 4 am... what's wrong with this picture?)