Those who travel to mountain-tops are half in love with themselves, and half in love with oblivion.

As de Saussure said, risk-taking brings with it its own reward: it keeps a "continual agitation alive" in the heart. Hope, fear. Hope, fear - this is the fundamental rhythm of mountaineering. Life, it frequently seems in the mountains, is more intensely lived the closer one gets to its extinction: we never feel so alive as when we have nearly died.

This is the human paradox of altitude: that it both exalts the individual mind and erases it. Those who travel to mountain tops are half in love with themselves, and half in love with oblivion.

The unknown is so inflammatory to the imagination because it is an imaginatively malleable space: a projection-screen onto which a culture or an individual can throw their fears and their aspirations. Like Echo's cave, the unknown will answer back with whatever you shout at it.