Finally, our definition implies that enhancement interventions attempt to improve specific human capacities and traits, rather than whole persons. Unlike such comprehensive personal-improvement strategies such as prayer, psychoanalysis, or “the power of positive thinking”, biomedical enhancements are, at best, a piecemeal approach to human perfectibility. As a result, most biomedical enhancements involve trade-offs.  If extended life span comes with prolonged frailty, or if enhanced altruism compromises survival skills, the overall value of the enhancement can be called into question (Shickle 2000).