Ayala F J
Department of Ecology and Evolutionary Biology, University of California, Irvine 92697-2525, USA.
Hist Philos Life Sci. 1999;21(1):3-33.
Knives, birds' wings, and mountain slopes are used for certain purposes: cutting, flying, and climbing. A bird's wings have in common with knives that they have been 'designed' for the purpose they serve, which purpose accounts for their existence, whereas mountain slopes have come about by geological processes independently of their uses for climbing. A bird's wings differ from a knife in that they have not been designed or produced by any conscious agent; rather, the wings, like the slopes, are outcomes of natural processes without any intentional causation. Evolutionary biologists use teleological language and teleological explanations. I propose that this use is appropriate, because teleological explanations are hypotheses that can be subject to empirical testing. The distinctiveness of teleological hypotheses is that they account for the existence of a feature in terms of the function it serves; for example, wings have evolved and persist because flying is beneficial to birds by increasing their chances of surviving and reproducing. Features of organisms that are explained with teleological hypotheses include structures, such as wings; processes, such as development from egg to adult; and behaviours, such as nest building. A proximate explanation of these features is the function they serve; an ultimate explanation that they all share is their contribution to the reproductive fitness of the organisms. I distinguish several kinds of teleological explanations, such as natural and artificial, as well as bounded and unbounded, some of which but not others apply to biological explanations.
刀、鸟的翅膀和山坡都有特定的用途：切割、飞行和攀爬。鸟的翅膀与刀的共同之处在于，它们是为其所服务的目的而“设计”的，这个目的解释了它们的存在，而山坡是由地质过程形成的，与它们用于攀爬的用途无关。鸟的翅膀与刀的不同之处在于，它们不是由任何有意识的主体设计或制造的；相反，翅膀和山坡一样，是自然过程的结果，没有任何有意的因果关系。进化生物学家使用目的论语言和目的论解释。我认为这种用法是恰当的，因为目的论解释是可以接受实证检验的假设。目的论假设的独特之处在于，它们根据一个特征所服务的功能来解释其存在；例如，翅膀的进化和留存是因为飞行对鸟类有益，增加了它们生存和繁殖的机会。用目的论假设来解释的生物体特征包括结构，如翅膀；过程，如从卵到成年的发育；以及行为，如筑巢。对这些特征的直接解释是它们所服务的功能；它们都共有的最终解释是它们对生物体繁殖适应性的贡献。我区分了几种目的论解释，如自然的和人工的，以及有界的和无界的，其中一些适用于生物学解释，而另一些则不适用。
