(12) john wants to marry a girl with green eyes

apart from anything else, john, like most of us at one time or another, may be subject to irrational and contradictory desires: he might resolutely maintain that he wants to marry somebody he does not want to exist.

it may be argued that, if john wants to marry a girl with green eyes, having no specific girl in mind, he must nonetheless want it to be the case that there is a girl with green eyes such that he marries her...

I do not find this argument at all persuasive.