744 LECTUUE LX. 



. Pythagoras, great as he was in some other departments of science, reasoned 

 r:speccing physical effects in a manner too mathematical and visionary, to 

 allow him much claim to he ranked among those, who have studied to inves- 

 tigate the minute operations of nature. 



, Anaxagoras was so far from confining himself to the supposition of four 

 elements, which was most generally received by the philosophers of antiquity, 

 that he imagined the number of elements nearly if not absolutely infinite. 

 He conceived that the ultimate atoms, composing every substance, were of 

 the same kind with that substance, and his system was thence called the 

 homoeomeria; it erred perhaps less from the truth than many of the more 

 prevalent opinions. Dcmocritus, adopting the sentimentsofLeucippus, proposed 

 a still more correct theory of the constitution of matter, supposing it to be 

 ultimatel}' so far homogeneous, that the weight of its atoms was proportional 

 to their bulk. He asserted that the forms of these atoms were different and 

 unalterable; that they were always in motion, and that besides their primi- 

 tive difference of form, they were also susceptible of a variety in the mode 



lof their arrangement. The space not occupied by the atoms of matter, he 

 considered as a perfect vacuum. 



As Thales had supposed water to be the first principle of all things, and 

 Anaximenes air, so Heraclitus fixed on fire as the foundation of his system, 

 attributing to it the property of constant motion, and deriving all kinds of 

 grosser matter from its condensation in different degrees. This doctrine was 

 wholly unsupported by any thing like reason or observation. 



Plato introduced into philosophy a variety of imaginations, which re- 

 sembled the fictions of poetry much more than the truths of science. 

 He maintained, for example, that ideas existed independently of the human 

 mind, and of the external world, and that they composed beings of different 

 kinds, by their union with an imperfect matter. It is observed by Bacon, in 

 his essay on the opinions of Parmenides, that the most ancient philosophers, 

 Empedocles, Anaxagoras, Anaximenes, Heraclitus, and Democritus, sub- 

 mitted their minds to things as they found them ; but that Plato made the 

 world subject to ideas, and Ajystotle made even ideas, as well as all other 

 things, subservient to words ; the minds of men beginning to be occupied, in 



