204 PHYSICAL SCIENCE IX THE MIDDLE AGES. 



2. Character of Commentators. The spirit of commentation, as lias 

 already been suggested, turns to questions of taste, of metaphysics, Oi 

 morals, with far more avidity than to physics. Accordingly, critics 

 and grammarians were peculiarly the growth of this school ; and, 

 though the commentators sometimes chose works of mathematical or 

 physical science for their subject (as Proclus, who commented on 

 Euclid's Geometry, and Simplicius, on Aristotle's Physics), these com- 

 mentaries were, in fact, rather metaphysical than mathematical. It 

 does not appear that the commentators have, in any instance, illus- 

 trated the author by bringing his assertions of facts to the test of 

 experiment. Thus, when Simplicius comments on the passage con- 

 cerning a vacuum, which we formerly adduced, he notices the argu- 

 ment which went upon the assertion, that a vessel full of ashes would 

 contain as much water as an empty vessel ; and he mentions various 

 opinions of different authors, but no trial of the fact. Eudemus had 

 said, that the ashes contained something hot, as quicklime does, and 

 that by means of this, a part of the water was evaporated ; others 

 supposed the water to be condensed, and so on. 3 



The Commentator's professed object is to explain, to enforce, to 

 illustrate doctrines assumed as true. He endeavors to adapt the work 

 on which he employs himself to the state of information and of opinion 

 in his own time ; to elucidate obscurities and technicalities ; to supply 

 steps omitted in the reasoning ; but he does not seek to obtain ad- 

 ditional truths or new generalizations. He undertakes only to give 

 what is virtually contained in his author ; to develop, but not to create. 

 He is a cultivator of the thoughts of others : his labor is not spent on 

 a field of his own ; he ploughs but to enrich the granary of another 

 man. Thus he does not work as a freeman, but as one in a servile 

 condition ; or rather, his is a menial, and not a productive service : 

 his office is to adorn the appearance of his master, not to increase his 

 wealth. 



Yet though the Commentator's employment is thus subordinate and 

 dependent, he is easily Jed to attribute to it the greatest importance 

 and dignity. To elucidate good books is, indeed, a useful task ; and 

 when those who undertake this work execute it well, it would be most 

 unreasonable to find fault with them for not doing more. But the 

 critic, long and earnestly employed on one author, may easily under- 

 rate the relative value of other kinds of mental exertion. He m.iy 



3 Simplicius. p. 170. 



