Deutero-Isaiah / multiple authorship of Isaiah — Mike skeptical

Mike is opposed to the Deutero-Isaiah hypothesis (First Isaiah = chapters 1–39, Second Isaiah = 40–66, written by a different author much later). He acknowledges the theory is held by some scholars. He notes that even if Second Isaiah were by a different author, it would not undermine Messianic prophecy about Christ since it would still predate Jesus by centuries. His main counter-argument: Jesus quotes from both halves of Isaiah and attributes both to Isaiah by name, implying single authorship. Mike says he cannot recall other specifics off the top of his head.