Harrison is a veteran scientific cosmologist. Now in his eighties, he offers his own personal perspective on the subject after many decades in the field. Much as John Wheeler (the great Princeton physicist now well over 90) was forced to look back on his subject after a recent heart attack, Harrison also takes a broader perspective on the subject.
For Harrison, cosmology is not just a scientific enterprise. Of course scientific cosmologists do scientific cosmology, and it is perfectly legitimate to do so. However in Harrison's view, there is the Universe and the universe. The Universe is what the philosopher might call 'Reality' beneath appearances, or the mystic or theologian would call God or the Absolute. Harrison divides the Universe into the universes which each person's worldview creates, whether they are scientists, poets, philosophers, theologians, or just ordinary people. Harrison's view is somewhat Kantian and he regards the Universe in itself as unknowable. He offers several interesting arguments to support this, including quotes from the writer of the mystical tract 'The Cloud of Unknowing.'
Harrison concludes that many scientific schemas have come and gone over the ages which purport to supply the 'grand theory' which will explain everything. He looks at the way some systems are adopted and others rejected and in a somewhat Kuhnian vein, adopts a position from Nicholas of Cusa he calls learned ignorance. This is an essentially humble approach to the universe, the belief that what we know is only the tiniest tip on an unfathomable iceberg of the unknown. There is no final theory and there never will be one, as the cosmos and its riches are infinite and will always be probed at ever new levels, so long as the human race lives.
This metaphysical argument is very interesting and has also been posed in other forms by physicists such as Paul Davies and mathematicians such as Roger Penrose (though applied to mathematical realities rather than the physical). The humility is somewhat refreshing in the face of the hubris which occurs in some scientists, who seem to look at all culture outside of science as deeply inferior to the way science contemplates the universe. While such an argument might be wrong (one day we may come up with a final theory) it is interesting to consider.