So just what is the third Great Invention of all time?

First we had agriculture, then the scientific method, now "

Worstall @ the Weekend So here's a fun little game for a Sunday morning: what was, or is, the third great invention of all time? I have a candidate for it and it's very much to do with what youse guys do all day. But I'm not entirely sure that it is the proper winner of third place: certainly, most economists wouldn't rate it there at all."