D'ALEMBEET. 447 



literary pieces, somewhat dogmatical with their shallow- 

 ness. His very definition of Eloquence is entirely 

 faulty ; he calls it the faculty of communicating to 

 others the feelings that fill our own minds ; according 

 to which, however dull or impotent these feelings may 

 be, their impression being truly conveyed, they pro- 

 duce all the effects of the highest eloquence, and so 

 every person may be eloquent nay, almost all may be 

 equally eloquent. His reflections on History are of no 

 higher merit. Of his notions respecting Poetry we 

 have already spoken. 



It remains to speak of his general treatise on the 

 4 Elements of Philosophy.' It is one of his best liter- 

 ary works, and certainly preferable to that which it 

 approaches nearest in the subject-matter, the Introduc- 

 tory Discourse to the Encyclopaedic. It is exceedingly 

 comprehensive ; it is rapid without being hurried or 

 hasty ; it is as clearly written as possible ; and it is 

 accompanied with illustrations judiciously given and 

 very convenient for the general reader. But though 

 it be well entitled to these commendations, it is not 

 easy to follow Condorcet in his eulogy of this piece 

 as containing an important " metaphysical discovery." 

 He regards it as settling for the first time the contro- 

 versy "whether the laws of motion belong to the class 

 of contingent or of necessary truths," and he considers 

 D'Alembert as having first discovered the demonstra- 

 tion that these laws are necessary. Now nothing can 

 be more certain than that D'Alembert does no such 

 thing as prove this position. He only shows, what 

 never could be doubted, that the deductions from cer- 

 tain assumed facts are necessary and not contingent. 

 Assuming the existence of matter, arid also its impene- 

 trability, he treats the vis inertias as demonstrated, and 

 also its corollary, the uniformity of motion once begun 

 and not affected by any external causes. But the im- 

 penetrability of matter is a contingent truth as well as 

 its existence ; and there is nothing in the definition of 



