The most important science to be done with a Hubble successor telescope could be the detection of extrasolar terrestrial planets and the search for life on those planets. A telescope which is optimized for terrestrial planet detection will also be a superb facility for ultraviolet-optical astrophysics, with a large collecting area, high angular resolution, and wide-band response. A coronagraphic Terrestrial Planet Finder (TPF) mission should be flown to explore the extrasolar planet frontier around nearby stars, much as Hubble was flown to explore the galactic frontier at the edge of the Universe.