Until the 1960s or so, aid climbing was normal practice in most climbing areas. But as improvements in technique and equipment meant that many aid routes could be climbed free, some influential climbers began to criticise the use of aid as being against the spirit of mountaineering. Reinhold Messner wrote, "Rock faces are no longer overcome by climbing skill, but are humbled, pitch by pitch, by methodical manual labour … Who has polluted the pure spring of mountaineering?" (from "The Murder of the Impossible").