John O. Reiss

In September 2008, 10 years after the untimely death of Pere Alberch (1954–1998), the 20th Altenberg Workshop in Theoretical Biology gathered a group of Pere’s students, col- laborators, and colleagues (Figure 1) to celebrate his contribu- tions to the origins of EvoDevo. Hosted by the Konrad Lorenz Institute for Evolution and Cognition Research (KLI) outside Vienna, the group met for two days of discussion. The meeting was organized in tandem with a congress held in May 2008 at the Cavanilles Institute for Biodiversity and Evolutionary Biology (ICBiBE) in Valencia, Spain. The talks at the KLI were equal parts: nostalgic remembrance, excitement over new ways of thinking about old problems, and an unrepressed vitriol against the resurgence of reductionist thinking in EvoDevo. Here we highlight some of the key aspects of Pere’s life and work that informed and infused the talks.

Human intentional action, including the design and use of artifacts, involves the prior mental representation of the goal (end) and the means to achieve that goal. This representation is part of the efficient cause of the action, and thus can be used to explain both the action and the achievement of the end. This is intentional teleological explanation. More generally, teleological explanation that depends on the real existence of a representation of the goal (and the means to achieve it) can be called representational teleological explanation. Such explanations in biology can involve both external representations (e.g., ideas in the mind of God) and internal representations (souls, vital powers, entelechies, developmental programs, etc.). However, another type of explanation of intentional action (or any other process) is possible. Given that an action achieving a result occurs, the action can be explained as fulfilling the necessary conditions (means) for that result (end), and, reciprocally, the result explained by the occurrence of those necessary conditions. This is conditional teleological explanation. For organisms, natural selection is often understood metaphorically as the designer, intentionally constructing them for certain ends. Unfortunately, this metaphor is often taken rather too literally, because it has been difficult to conceive of another way to relate natural selection to the process of evolution. I argue that combining a conditional teleological explanation of organisms and of evolution provides such an alternative. This conditional teleology can be grounded in existence or survival. Given that an organism exists, we can explain its existence by the occurrence of the necessary conditions for that existence. This principle of the 'conditions for existence' was introduced by Georges Cuvier in 1800, and provides a valid, conditional teleological method for explaining organismal structure and behavior. From an evolutionary perspective, the conditions for existence are the range of boundary conditions within which the evolutionary process must occur. Moreover, evolutionary change itself can be subjected to conditional teleological explanation, because natural selection theory is primarily a theory about the relation between the conditions for the existence of organisms and the conditions for the existence of traits in populations. I show that failure to distinguish representational from conditional teleological explanation has confused previous attempts to clarify the relation of teleology to biology