The recent development of unified theories of active galactic nuclei (AGN)has indicated that there are two physically distinct classes of these objects -radio-loud and radio-quiet. The primary observational distinctions between thetwo types are: (1) The radio-loud objects produce large scale radio jets andlobes, with the kinetic power of the jets being a significant fraction of thetotal bolometric luminosity. On the other hand, the weak radio ejecta of theradio-quiet objects are energetically insignificant. (2) The radio-loud objectsare associated with elliptical galaxies which have undergone recent mergers,while the radio-quiets prefer spiral hosts. (3) The space density of theradio-louds at a given optical luminosity is $\approx$ 10 times lower than thatof the radio-quiets. Despite these differences, the (probably) thermalemissions from the AGN (continua and lines from X-ray to infrared wavelengths)are quite similar in the two classes of object. We argue that this last resultsuggests that the black hole masses and mass accretion rates in the two classesare not greatly different, and that the difference between the classes isassociated with the spin of the black hole. We assume that the normal process of accretion through a disk does not leadto rapidly spinning holes, and propose instead that galaxies (e.g. spirals)which have not suffered a recent major merger event contain non-rotating oronly slowly rotating black holes. When two such galaxies merge, the two blackholes are known to form a binary and we assume that they eventually coalesce.In the small fraction of mergers in which the two ``parent'' galaxies containvery massive holes of roughly equal mass, a rapidly spinning, very massive holeresults. It is proposed that such mergers are the progenitors of powerful radio
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