This chapter discusses prismatic history a selective, select account of theory building in the field, which ideally stirs gerontological imaginations about future theoretical work. Several of gerontology’s founders promulgated or borrowed theories to guide research on aging. Based on work in pathology, cytology, and immunology, Metchnikoff formulated ‘phagocytosis‘, an interdisciplinary theory of aging hypothesizing that large intestinal white blood cells destroyed microbes that hastened premature senility in humans, apes, dogs, and plants; the construct anticipated various degenerative and wear-and-tear theories. Biologist Vincent Cristofalo, endorsing no unified biological theory of aging, reduced models into groupings of stochastic and developmental-genetic theories. Gerontologists demolished disengagement theory in Unripe Time. Not even a giant like Robert Havighurst could salvage parts of activity theory in order to sustain his pioneering theory of successful aging.