Monte Johnson

For an Aristotelian observer, the halo is a puzzling phenomenon since it is apparently sublunary, and yet perfectly circular. This paper studies Aristotle's explanation of the halo in Meteorology III 2-3 as an optical illusion, as opposed to a substantial thing (like a cloud), as was thought by his predecessors and even many successors. Aristotle's explanation follows the method of explanation of the Posterior Analytics for "subordinate" or "mixed" mathematical-physical sciences. The accompanying diagram described by Aristotle is one of the earliest lettered geometrical diagrams, in particular of a terrestrial phenomenon, and versions of it can still be found in modern textbooks on meteorological optics.

Isocrates' Antidosis ("Defense against the Exchange") and Aristotle's Protrepticus ("Exhortation to Philosophy") were recovered from oblivion in the late nineteenth century. In this article we demonstrate that the two texts happen to be directly related. Aristotle's Protrepticus was a response, on behalf of the Academy, to Isocrates' criticism of the Academy and its theoretical preoccupations. Contents: I. Introduction: Protrepticus, text and context II. Authentication of the Protrepticus of Aristotle III. Isocrates and philosophy in Athens in the 4th century IV. The Protrepticus of Aristotle as a response to the Antidosis of Isocrates V. Conclusion: dueling conceptions of philosophy, still dueling.