Abstract

  If temperature does not vary from one generation from to the next but its value is crucial for the development of particular phenotypic characteristics, a long-term change in its value may trigger major evolutionary changes of the organism. If a bird's nest maintains the critical temperature, then a statement that the bird is the nest's way of making another nest is as helpful as accounts couched in terms of genes' intentions. However, the language of intentions rests on different evidence and assumptions from causal language and the languages are not interchangeable. Understanding ontogeny in causal terms requires explanations that are made as simple as possible but not so simple that they become completely unrealistic