Few things are harder to understand than why we do what we do. In fact, most psychologists would agree that it is virtually impossible for a person to understand his or her own motivation - and consequently that it is not possible to understand the full scope of motivation of another person. Therefore it would be asking too much from this book to give an answer to the question why we do what we do.
What the book does is summarize findings in the psychology of self-determination and intrinsic motivation, the main fields of research of the author, who has published two books on this subject previously.
Deci starts from the position that individuals have something that can be called a "true self," and that people wish to act in accord with this "true self." They wish to be autonomous (authentic) rather than controlled. If they act autonomously (authentically), they are self-motivated. If they act autonomously, they also respect others because the "true self" wishes to be related to others (a point on which Aristoteles would have agreed, and Thomas Hobbes would have strongly disagreed). Deci assumes that human beings are cooperative by nature, rather than competitive.
The "true self," of course, is an artificial construct, a theory. And even if we assume that there is such a "true self," it is conceivable that there are people whose "true self" is competitive as well as people whose "true self" is cooperative. Some people may simply enjoy open confrontations whereas other people may abhor disharmony and clashes. Deci's book is mostly silent about such issues of personality, and his assumption that the "true self" is expressive of human connectedness is just that - a very general assumption.
Deci's book builds on the theories of an American school of psychology called "Humanistic Psychology." One of the most important proponents of this school was Abraham Maslow (1908-1970) who pioneered the concept of "self-actualization," a technical term for what Nietzsche once called "becoming who you are." Maslow's book "Motivation and Personality" (1954) is still well worth reading.
So, what does this book tell us if it does not tell us why we do what we do? It tells us - quite convincingly - that control is always second-best to autonomy. Deci's core thesis is that "self-motivation, rather than external motivation, is at the heart of creativity, responsibility, healthy behavior, and lasting change," (9) and that "social contexts that support and affirm people's perceived autonomy and perceived competence enhance intrinsic motivation, while social contexts that diminish people's perceived autonomy and perceived competence undermine intrinsic motivation." (81)
This is not exactly rocket science, but it gets interesting when Deci delves into the details of what "autonomy support" means - not permissiveness, but being clear, consistent and setting limits in an understanding, empathic way. He spells this out on about twenty pages in Chapter 10 titled "How to Promote Autonomy," and I would love to make these pages required reading for parents and managers.
In the nature-nurture debate, Deci's focus lies on the nurture side: "Although the social context is ENORMOUSLY important in affecting people's motivation and behavior, people's personalities ALSO affect their motivation and behavior" (184; italics are mine). In fact, Deci is largely silent about matters of personality, or defines it simply as "autonomy orientation," whereas he discusses the impact of the social context at length.
I am very much a fan of humanistic psychology, which has seen its heyday in the 1960s. It conveys important insights into the impact of "nurture" on human beings. But the assumptions of humanistic psychology about what constitutes human nature appear quite unfounded in the 21st century. To make claims about human nature without recourse to genetics, evolutionary theory, twin research, or the biochemistry of the brain is rather futile. In this respect "Why We Do What We Do" is definitely behind the curve (to make up for this I recommend Matt Ridley's "Nature via Nurture: Genes, Experience and What Makes Us Human" (2003) - popular science writing at its best and quite an education).
