The pessimist calls the glass half-empty. The optimist describes it as half-full. So what does the realist say? That the glass contains 50 per cent liquid and 50 per cent air? Well, surely. But that glass, if it has recently been drunk from, may well be drained dry before long. While if it is in the hands of a bar tender, being held under an upturned bottle, it will surely be full very soon. Every full glass will eventually become empty again and every empty glass is surely destined in time to fill once more. Faith is not misplaced now.