They same could be said of flight, but now we have machines whose sole purpose is flight. "Pure" is a bit of an extreme word, but clearly designed things are p

They same could be said of flight, but now we have machines whose sole purpose is flight. "Pure" is a bit of an extreme word, but clearly designed things are purer to particular goals than biological systems typically are. This is partly due to the essences of what design means and partly because machines don't have to do all the things biology does, such as maintain a metabolism that continually turns over their structural parts, reproduce, find and process their own fuel, etc.