Here Astell seems to be saying that if her audience is prejudiced against her, has already set in their minds that her task is impossible, then she'll get nowhere. Nice insight into the nature of the audience and their receptivity. Sometimes a fight is lost before it's ever begun, though that doesn't mean to stop trying. There's always another audience, one brought on by another exigence, context, or cultural technique (although below, she seems to be insisting that there's some kernel of perwasive opportunity left to her, can she but root it out).

We know it's serious business because of the W.