Which appeal suggests that a proposal should be distrusted simply because of its source?

The appeal that suggests a proposal should be distrusted simply because of its source is the appeal to prejudice. This type of reasoning occurs when the focus shifts from the merits of an argument to the characteristics or biases of the person presenting the argument. Instead of evaluating the proposal based on its content, this appeal encourages rejection based solely on who is making the claim, often playing on preconceived notions or biases about the source.

In the context of argumentation, this can undermine rational discourse and objective analysis, as it diverts attention from the actual argument and relies on emotional or biased responses towards the source itself. This aspect of the appeal emphasizes how important it is to critically assess arguments based on their validity and logic rather than the reputation or background of the individual or group proposing them.