Abstract
Over the past several decades, philosophical analyses have shown that reasoning about purposes in nature is epistemically respectable. However, less attention has been paid to the heterogeneity of aims and commitments that motivate inquiry into apparent purposiveness. Our aim in this paper is to map major contours of the landscape of biological teleology and show how the resulting epistemic precision yields payoffs for different lines of scientific inquiry. We begin with the distinction between intrinsic and extrinsic forms of teleology (Lennox 1992). Roughly, teleology is intrinsic if purposes arise from some set of properties or relations internal to a system (typically an organism). By contrast, teleology is extrinsic if purposes manifest as a consequence of properties or relations external to a system. The intrinsic/extrinsic distinction has traditionally marked different answers to an ontological question (“what is teleology?”). Yet we treat it as a springboard for making several epistemological observations. First, attributions of intrinsicality or extrinsicality presuppose a system-environment circumscription, but the criteria on which this is based are typically left unanalyzed. Second, they assume that systems are composed of parts that contribute to a characteristic activity or organizational pattern. However, these parts can themselves be treated as teleologically organized wholes in a nested fashion, complicating the analysis. Third, the timescale on which systems manifest purposiveness can be highly variable and is often implicitly keyed to what counts as a whole system, its parts, and relevant features of the environment. These distinctions impact how teleology is modeled and explained in living systems. For example, the boundaries between system and environment can be drawn differently depending on what question is in view (e.g., “what is the source of directionality underlying goaldirectedness?”; “what accounts for the properties of self-maintenance and autonomy in living systems?”). This, in turn, yields different perspectives on what counts as “intrinsic” versus “extrinsic.” Likewise, since research on teleology has multiple aims—prediction, characterization, explanation, and control—which part-whole relations are salient may vary (e.g., a part useful for prediction may be unhelpful in characterizing purposive behavior). More finegrained distinctions reveal additional contours of the epistemic landscape, such as whether purposiveness is explanans or explanandum. Different criteria of adequacy are associated with these aims, such as accounting for what makes living systems distinctive versus offering a unified account of goal-directedness in biology and culture. These differences lead researchers to assign different meanings to shared concepts (e.g., organization) and metaphors (e.g., design), and to adopt divergent modeling strategies, like abstracting away from the environment to model intrinsic dynamics (or vice versa). This complex possibility space implies that traditional controversies may reflect research communities with different priorities talking past one another. Teleology is a multi-faceted phenomenon that involves questions of adaptation, functionality, goal-directedness, agency, and organization. The epistemic precision derived from this mapping exercise thus has immediate payoff. We illustrate the final point by showing how our analysis illuminates modeling and explanation choices for two divergent accounts of biological purposiveness (McShea 2012; Mossio and Bich 2017).
