The heart of their theory is this: People are not closed, self-contained creatures that interact with other similarly isolated beings; instead their bodily functions are interconnected and physically altered by their relationships with others. That is why, they contend, if one half of a couple leaves on a trip, the partner left behind may suffer a cold that would have been staved off had the pair (and their immune systems) been together. As the authors point out: ''Who we are and who we become depends, in part, on whom we love.''
In elegant prose that keeps the dry scientific jargon to a blessed minimum, they argue why certain widely held societal beliefs (career success equals happiness; being ''in love'' means the ''sparks'' never disappear) clash with biological reality -- and why we need a culture attuned to the ways of the heart.
