That's just the simple sequential sense of "first," the first that comes before second, third and fourth; but there's something more radical here than the ordinal or sequential sense of "first."

这只是“先“表示顺序的简单含义,先于第二，第三，第四的那个“先“，但这里,“先“除了表示顺序的意思外还有更激进的含义“

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