What makes life meaningful?

This week, the dome of St Paul's Cathedral is being used as a canvas for an artwork commissioned by the Dean called The Question Mark Inside.

"The project seeks to answer the question: ‘what are the things that make modern life meaningful and what does St Paul’s mean in that contemporary context?to us in 2008?'. A stream of possible answers will appear as text projections onto the South elevation of the cathedral dome, the West Front at Ludgate Hill and inside onto the Whispering Gallery. The Question Mark Inside marks the 300th anniversary of the topping out of the Cathedral."

(Don't read anything into my selection of this word - one among many in several languages - I was having great difficulty with my little Canon, this one has the least camera shake)