In a highly speculative analysis, Edinburgh University developmental psychologist Donaldson (Children's Minds, 1979) proposes an unusual model of human mental processes, viewing them as a series of distinct yet interactive stages, and charting a course from birth to maturity to account for the evolution of both feelings and thoughts. Building on the work of Freud and Piaget, the developmental structure erected here has four ``modes,'' each defined by a specific ``locus of concern.'' The ``point'' mode, first observed in eight-week-old infants, has its locus in the ``here and now'' and is followed within months by the ``line'' mode, in which the child becomes able to differentiate immediate experience from that in other places and time periods, shifting its concern from ``here and now'' to ``there and then.'' Further maturation brings about the ``construct'' mode, which permits increasingly abstract conceptualization in a locus of ``somewhere, sometime,'' until a final, ``transcendent'' stage is reached in which the concerns of space-time are largely irrelevant. Variations of these primary stages exist, Donaldson says, as several main components-- perception, action, emotion, and thought--interact and come into play, with each mode active not only in adult experience but in the experience of the species as well. Donaldson assesses the impact of the Age of Enlightenment on human evolution from the modal standpoint, moving on to compare the respective contributions made by Western thinkers from Plato to Descartes and by Buddhist precepts as a means of dealing with emotional and intellectual needs--but she handles the broader sociocultural issues with far less precision than she uses in constructing the developmental model. Ambitious and challenging but, ultimately, more suggestive than persuasive--and, at times, tough going for the general reader.