(p. 329) They debated the grammatical issue: If “different” was supposed to modify the verb “think,” it should be an adverb, as in “think dif-(p. 330)ferently.” But Jobs insisted that he wanted “different” to be used as a noun, as in “think victory” or “think beauty.” Also, it echoed colloquial use, as in “think big.” Jobs later explained, “We discussed whether it was correct before we ran it. It’s grammatical, if you think about what we’re trying to say. It’s not think the same, it’s think different. Think a little different, think a lot different, think different. ‘Think differently’ wouldn’t hit the meaning for me.”
Isaacson, Walter. Steve Jobs. New York: Simon & Schuster, 2011.