Twenty-five years ago Paul Wilpert called for a thorough re-examination of our knowledge of the content of Aristotle's lost work De Philosophia. Expressing his reservations about the validity of our current reconstruction of the work, he wrote: ‘On the basis of attested fragments, we form for ourselves a picture of the content of a lost writing, and this picture in turn serves to interpret new fragments as echoes of that writing. So our joy over the swift growth of our collection of fragments is clouded by the thought that we are not thereby really nearing the original character of the work, but we are entangling ourselves ever more tightly in a picture we ourselves have created.’ As a corrective Wilpert called for a critical retracing of our steps since 1830 to establish a more secure reconstruction of this important lost work.
Since then there have been numerous, searching analyses of the ideas and fragments of De Philosophia, but at least one venerable old theory has escaped critical reappraisal: namely, the theory that in De Philosophia Aristotle discussed his doctrine of a fifth element, i.e. his belief that the heavenly bodies are composed of an element distinct from the four earthly elements, earth, water, air, and fire. This theory has become so widely accepted that it has virtually become a fact. When support is needed, most modern authors simply cite one or both of the two modern authorities on the early Aristotle, namely W. Jaeger and E. Bignone. The more meticulous restate the traditional evidence with complete confidence that this evidence proves their case. If Wilpert's hope for a firmly grounded reconstruction of the De Philosophia is ever to be achieved, one of the important desiderata today is a critical re-examination of the evidence for the fifth element in this work.