Final answer:
The statements in the passage are designed to persuade by demonstrating the ineffectiveness of past efforts, building credibility, and engaging the audience to consider a decisive action.
Step-by-step explanation:
The passage in question aims to persuade the audience by emphasizing a sense of urgency and the exhaustion of all previously attempted methods of argumentation and plea. The speaker is highlighting that logical arguments ("argument"), emotional appeals ("entreaty and humble supplication"), and thorough discussions ("held the subject up in every light") have all been ineffective. This indicates that the situation is dire and requires immediate action, as conventional methods have failed. The effect of these statements is to build the speaker's credibility through appeals to emotion and to engage the audience in a way that calls for a response. The use of rhetorical questions also involves the audience directly and solicits their agreement that a new course of action might be necessary. Overall, the persuasive effect of these statements is to demonstrate the seriousness of the issue and motivate the audience towards change.