The design of Rhetoric is to remove those Prejudices that lie in the way of Truth, to Reduce the Passions to the Government of Reasons; to place our Subject in a Right Light, and excite our Hearers to a due consideration of it.

In this quote, Mary Astell defines the purpose of rhetoric as a tool to clear the way for truth by addressing and removing any prejudices that might distort people's understanding. Astell emphasizes that effective rhetoric should help people see a subject from an objective perspective, stripping away biases or preconceived notions that might cloud their judgment. By focusing on truth, rhetoric serves as a means of clarification, helping audiences approach an issue with a clear and open mind.

Astell also argues that rhetoric should serve to reduce the passions of individuals, steering them toward the government of reason. This implies that emotional reactions and impulsive feelings can often lead to irrational decisions or judgments, and it is the role of rhetoric to temper these emotions in favor of more rational and reasoned thinking. In other words, rhetoric should guide people from emotional responses toward thoughtful and logical consideration.

Furthermore, Astell suggests that rhetoric has the power to present a subject in the right light by framing it in a way that helps listeners or readers properly understand it. The goal is not just to persuade, but to help people see the issue clearly and make informed decisions based on reason and truth. This reflects a belief in the ethical potential of rhetoric to contribute positively to discourse, rather than manipulate or deceive.

Ultimately, Astell’s quote emphasizes the role of rhetoric in fostering clearer, more reasoned thinking by overcoming biases, controlling emotions, and presenting ideas in their most accurate form. For Astell, the ideal use of rhetoric is not to deceive or manipulate, but to engage in a way that leads to better understanding and thoughtful action.