String theory offers a viable theory of quantum gravity, with spin 2 gravitons encoded in closed strings. But the failure to find evidence for supersymmetry at the LHC has left string theory in disarray. A solution to the problem is in plain sight: revert to old-fashioned, 1970s-style, nonsupersymmetric, bosonic string theory, reenvisaged as a theory of all the forces, not just the strong force. The old theory correctly reproduces the Brauer-Weyl (1935) algebraic relation between fermions and bosons seen in the standard model, whereas supersymmetry does not. Sages of string theory commonly reject bosonic string theory on the grounds that (1) it does not admit fermions, and (2) its ground state is tachyonic. But rejection (1) assumes that fermions are strings, wheres the fermions of bosonic string theory are the endpoints of strings, and are not themselves strings; in modern parlance, the fermions are excitations of the D-brane boundary of strings. As to rejection (2), the properties of the tachyon are precisely those of a Higgs field: it is a multiplet of the unbroken symmetry; the "vacuum" state where the Higgs field vanishes identically is tachyonically unstable; and it has spin zero. I propose Clifford(11,1) string theory, a 26-dimensional, tachyonic, bosonic, open string theory, whose bosons occupy all 26 dimensions while their fermionic endpoints are confined to an 11+1 dimensional D-brane. The 26 dimensions compactify to 12 on the 14-dimensional self-dual torus of the rank 14 SU(8)xSU(8) subgroup of the group G^2(10)=U(16) generated by Clifford(11,1) multivectors of grade 2 (mod 4).
Clifford(11,1) string theory