Agency, goal directedness, and the levels of biological organization.

Life and evolution often appear purposeful, but goals and purpose are not parts of reductionist sciences (e.g., modern physics, chemistry). This contradiction has been an enduring conundrum. Traditionally, explanations that invoke goal directedness and agency have been treated cautiously, but a new move argues that we should recognize multiple levels of biological organization-cells, tissues, and organisms-as agents with agendas. In the present article, we offer clarity on when and why the concept of goal directedness is applicable in biology. We offer grounds for distinguishing whether something is a candidate for goal directedness, and we consider whether explanations involving goal directedness (teleonomic explanations) are useful. Teleonomic explanations can be briefer and less computationally demanding than algorithmic explanations, and they can help pose hypotheses for how something might function. However, they risk omitting critical details and misdirecting conclusions. Therefore, although there is a place for goal-directed explanations in biology, they should be used with care.