What is an appeal to logic and reason in a speech or written work?

Compose a one-paragraph persuasive message board post about grendel.

[he] let his gaze wander to the swirling water of the stream racing madly beneath his feet. a piece of dancing driftwood caught his attention and his eyes followed it down the current. how slowly it appeared to move! what a sluggish stream! what contrasting words are used to describe the stream in this passage?

Which quotation best supports the authors’ claim and purpose?