The phrase 一无所获 is formed through a logical, almost mathematical layering of negation and scope. It begins with "一" (one) to establish a minimal, singular unit, then applies "无" (to not have) to entirely negate its existence. This combination of "一无" creates the sense of "not even one". That absolute negation is then directed specifically by "所" toward the act or result contained in the final character "获" (to gain or acquire). Thus, the construction moves from a universal negation ("not a single thing") to a focused target ("within the realm of what was sought"), resulting in the complete meaning: to have gained nothing at all from one's efforts.