Berkovits, NathanVafa, Cumrun2019-09-221994BERKOVITS, NATHAN, and CUMRUN VAFA. 1994. “ON THE UNIQUENESS OF STRING THEORY.” Modern Physics Letters A 9 (7): 653–63. https://doi.org/10.1142/s0217732394003889.0217-73231793-6632http://nrs.harvard.edu/urn-3:HUL.InstRepos:41385044We show that bosonic strings may be viewed as a particular class of vacua for N = 1 superstrings, and N = 1 superstrings may be viewed as a particular class of vacua for N = 2 strings. Continuing this line of string hierarchies, we are led to search for a universal string theory which includes all the rest as a special vacuum selection.en-USJournal Article2019-09-2210.1142/S0217732394003889