where, in seeking the most general cosmological solutions of Einstein’s equations using rigorous applied mathematics techniques (see also Eardley, Liang and Sachs 1971), they found the inhomogeneous mixmaster universe (the ‘generalized’ Kasner solution) as representing a generic behavior near the cosmological singularity. This also paralleled the work of Ellis and MacCallum (1969) who, following Taub (1951) and Heckmann and Schucking (1962), gave a detailed analysis of the group-theoretical structure of the Bianchi cosmologies. Misner’s chaotic cosmology program provided the physical rationale for these studies. It also prepared the ground for minisuperspace quantum cosmology (1969b, 1972).

Third, the establishment of the quantum cosmology program, which includes the application of the ADM quantization (1962) to cosmological spacetimes, and the adaptation of the Wheeler- DeWitt superspace formulation of quantum gravity (Wheeler 1968, De Witt 1967) to minisuperspace cosmology. The physical motivation was to understand ‘the issue of the initial state’ (Wheeler 1964), and, in particular, the quantum effects of gravity on the cosmological singularity. It was Misner and his associates who started the first wave of activity in quantum cosmology (Ryan, 1972; see also Kuchar 1971, Berger 1974, 1975). The second wave, as we know, came with the work of Hartle and Hawking 