Food for thought

There is a short passage from a book I read a while ago by Jon Steel called ‘Truth. Lies & Advertising’ that I thought I'd post - it’s actually a quoted passage from a the book by Norman MacLean ‘ The River Runs Through It’, it goes like this:

He said, “They are feeding on drowned yellow stone flies.”
I asked him, “How did you think that out?”
He thought back on what had happened like a reporter;
He started to answer, shook his head when he found he was wrong, and then started out again. “All there is to thinking,” he said, “is seeing something noticeable which makes you see something you weren’t noticing which makes you see something that isn’t even visible”.
I said to my brother.” Give me a cigarette and say what you mean”.