There is no single correct meta-theory, just as there is no single correct definition of development. Even the developmental systems approach has its drawbacks. However, as research accumulates, many theories derived from certain meta-theories have been found to be incomplete—so far researchers have not found any significant aspect of development that is caused only by nature or only by nurture. Therefore, most researchers currently say they favor interactive metatheories, like organismic, contextualist, or systems meta-theories. However, it is important to look carefully at researchers’ (and our own) actual work, because sometimes we find one meta-theory most compatible with our own assumptions about humans and how they develop, but nevertheless our research (sometimes surprisingly) seems to be more consistent with the assumptions from a different meta-theory, even one we would say that we disagree with in principle.