This is the basic definition of a warrant I use with my students: a warrant explains how the evidence supports the claim (claims differ from thesis in that a claim supports a thesis; a claim operates at the paragraph level while a thesis operates at the essay level)
The idea that a warrant examines the underlying assumptions of the relationship between the claim and the evidence, the standard definition provided for a warrant, can be confusing at first. For this reason, I start with the above definition and, if a class is ready for it, I present them with the actual definition discussed below.
At the bottom of this page, find highlighted a discussion of the ethical implications of the lack of warrants in advertisements that may be useful in framing a discussion for lang and lit papers
Good for practicing identifying underlying assumptions in others writing. Excellent because it asks the reader to determine the validity of the warrant.