From Your Face Tomorrow: Fever and Spear by Javier Marias:
In one respect--but only one--Tupra reminded me of my father, who never allowed us, my siblings and me, to be satisfied with what appeared to be a dialectical victory in our debates, or a success in explaining ourselves. "What else," he would say when we had assumed, exhausted, that an exposition or an argument was over. And if we replied: "Nothing. That's it. Isn't that enough?", he would reply, to our momentary wild despair: "Why, you haven't even started yet. Go on. Quickly, hurry, keep thinking. Having an idea, or identifying it, is something, but then again, once absorbed, it's almost nothing: it's like arriving at the first, most elementary level, which, it's true, is more than most people ever do. But the really interesting and difficult thing, the thing that can prove both truly worthwhile and very hard work, is to continue: to continue thinking and to continue looking beyond what is purely necesssary, when you have the feeling that there is no more to think and no more to see, that the sequence is complete and that to continue would be a waste of time. In that wasted time lies the truly important, in the gratuitous and apparently superfluous, beyond the limit where you feel satisfied, or where you get tired or give up, often without even realising it. At the point where you might say to yourself there can't be anything else. So tell me, what else, what else occurs to you, what else can you bring to the argument, what else can you offer, what else have you got? Go on thinking, quickly now, don't stop, go on."