One of the most important themes in the history of civilization is our ever increasing use of tools to shape and control the world around us. These tools range from the simple hammer and saw of the carpenter to all the complex machine of our modern civilization. We use tools to extend our power. Tools allow us to engage in activities for which mankind's bodies are totally unsuited, such as traveling through the air, or beneath the surface of water. Until recently, almost all tools served to extend the power of our bodies rather than those of o ....