When evaluating sources for English I, consider the following:
When writing an argumentative paper, it's okay for your sources to have strong opinions on the matter. When evaluating opinions, consider the evidence the author is giving to back up their point. If no evidence is given, consider whether their logic is sound? Not sure? Check out this infographic on logical fallacies by Michele Rosenthal.
Also, consider your own biases when evaluating a source. Do you agree with an author because of their strong evidence and logic or because they are confirming what you already believe? Check out this page for more examples of cognitive biases.
by: Kris Straub