Every reader of this passage must spend the whole of his waking life looking at things. Looking, like breathing, is natural; we do it without noticing it. Looking is passive--but seeing is active. Once you start seeing things you really begin to wake up. People who see things which others have only looked at, and draw conclusions from what they see, can add to man's knowledge and help progress. Someone recently discovered a place where metal had been worked continuously longer than any where else in prefix = st1 /England. He "saw" a wall in theForestofDean. Thousands of people must have looked at it without really seeing it, but this man noticed that among the usual stones of that place were bits and pieces of a different color1; they also felt different to the hand. A closer sight showed that these pieces had been left behind in the fires of ancient people who had melted rocks to get metals. Looking around, he found more and more information, until the history of what men had done at that place over tens of centuries was known. For the writer "seeing" means   _  .
noticing things which need explaining doing something natural looking at things doing something without noticing it