De Lacey is the Parisian-turned-blind-peasant who lives in a cottage with his son and daughter. He's a nice old man: "descended from a good family in France" (14.2), he's the only person we meet who treats the monster kindly. (Okay, that's because he's blind. But still.)
Aside from giving us a warm and fuzzy juxtaposition to the monster's isolation, De Lacey gives us hope for humanity. He sympathizes with the monster's unhappiness, telling him not to despair, (optimistically) insisting that "the hearts of men … are full of brotherly love and charity" (15.24), and saying that it will "afford [him] true pleasure to be in any way serviceable to a human creature" (15.30).
Of course, this Disney moment screeches to a halt when the kids come back. Gee. It's too bad that we're not all blind.