 After expanding the numbers of Heaven and Earth, we find that the ones that are of benefit to us number fifty, and of these we actually use forty-nine, thus leaving one unused. Although this one is not used, yet through it the use of the other numbers becomes readily possible, and, although this one is not one of the numbers, yet through it the other numbers are formed. As this one represents the supreme ultimate of change, the other forty-nine constitute the ultimate of numbers. Non-being [wu] cannot be brought to light by means of non-being [wu] but must take place through being [you]. Therefore, by applying ourselves constantly to this ultimate among things that have being [you], we shall surely bring to light the primogenitor from which all things derive. (Lynn 1994: 60–61, with modifications)