Natural-Historical Collections. dS^l 



one on meteorology, in which mention is also made of minerals, and one on co- 

 lours ; 2dly, Two books on the generation and composition of bodies, that is, on 

 the motion of decomposition and recomposition of organized bodies ) ten on the 

 history of animals, four on their parts, one on the means of progression, two on 

 their generation, and various treatises on waking and sleeping. 



In all these works, Aristotle follows the same course as in his poetics, morals 

 and politics, that is, he lays down no rule, a priori, but deduces them all from 

 the observation of particular facts and their comparison. This method is but the 

 application of his theory of the origin of general ideas, which is opposed to that 

 of Plato. The latter, as we have said in analizing his Timaus, admits that the 

 general ideas exist by themselves, aud maintains that they are innate in man, in 

 other words, that his mind possessed them when it was united to the divinity, 

 and that when it finds them again, it is by a true reminiscence. The evident 

 consequence of, this system is to condemn the senses to inaction, in order to fa- 

 vour the return of the mind by recollection towards its former state. Aristotle 

 opposes this doctrine. With him there are no innate ideas. It is of the na- 

 ture of the divinity to possess of itself all the general ideas ; but man can only 

 acquire them by abstraction, and as nothing occurs in his mind which has not 

 first passed through his senses, all his knowledge necessarily takes its source in 

 observation and experiment. From the simple fact of having laid down this 

 principle in his logic, his whole philosophy assumes a peculiar character, and he 

 has always the same mode of proceeding in the moral as in the physical sciences. 

 For example, when he has to write on politics, instead of first creating an ideal 

 republic, which serves him as a type, a term of comparison by which to judge of 

 the goodness of the different existing governments, he begins with bringing toge- 

 ther a great number of constitutions, compares them together, examines their in- 

 fluence on nations as made known by history, and at length arrives at general 

 views respecting the effects of social institutions and the resources of states. This 

 is the general method followed by Aristotle. It was necessary for us to make it 

 known before proceeding to the examination of his treatises on the natural sciences. 

 • Of those which we have enumerated, the first, which refers to general physics, 

 is the weakest of all, as might have been expected. In fact, any great progress 

 in that science cannot be made by attending merely to the facts which naturally 

 present themselves, it being necessary, moreover, to experiment. Now, in Aris- 

 totle's time, this could not be done, for the arts were not sufficiently advanced to 

 supply the means. There were only a few observations in unconnected groups, 

 and it was impossible to generalize them in a high degree. Many principles laid 

 down by our philosopher have been since found to be false or imperfect ; but then 

 they were truly the general expression of the phenomena known. He saw, for 

 example, solid or liquid bodies fall towards the ground when they ceased to be 

 supported, gaseous bodies rise trom the bottom towards the surface of water, and 

 flaiTie direct itself towards the sky ; and he conchided, that air and fire have a 

 tendency to ascend, earth and water to descend. We now know that these dif- 

 ferent motions are merely the result of a single power ; but we only arrived at 

 this discovery after new facts had shewn us the insufficiency of the first explana- 

 tions. The same remark applies to the principle of the horror vacui, which has 

 been so much ridiculed. Aristotle did not establish it a priori, but announced 

 it as being the general expression of the facts known at that epoch. Had he 

 seen water stopping in pumps at the height of 32 feet, and mercury rising in the 

 Torricellian tube to that of 28 inches, perhaps, or comparing the specific gravities 

 with the heights of the two columns, he might have been led to discover the true 

 cause of the phenomenon. We may observe, that so long as experiment had not 

 shewn the contrary, it was just as rational to suppose a disposition in bodies to 

 pass wherever a vacuum had been operated, as to admit that they have a mutual 

 attraction, which is now the opinion. The principle of the abhorrence of a va- 

 cuum has been found false ; but it has nothing absurd in itself, and it could only 

 seem so to persons who give a literal meaning to a figurative expression, which 



