A vigil in France for victims of the Charlie Hebdo attack. In cities across the world, pens and signs reading I Am Charlie were held aloft in honor of those killed in the gun attack. (AFP/Thierry Zoccolan)
A vigil in France for victims of the Charlie Hebdo attack. In cities across the world, pens and signs reading I Am Charlie were held aloft in honor of those killed in the gun attack. (AFP/Thierry Zoccolan)

Charlie Hebdo attack unites France on free expression, but will solidarity hold?