BOOK I.] APHORISMS. 403 



Again, when man reflects upon the entire liberty of nature, he 

 meets with particular species of things, as animals, plants, mine 

 rals, and is thence easily led to imagine that there exist in nature 

 certain primary forms which she strives to produce, and that all 

 variation from them arises from some impediment or error which 

 she is exposed to in completing her work, or from the collision 

 or metamorphosis of different species. The first hypothesis has 

 produced the doctrine of elementary properties, the second that 

 of occult properties and specific powers ; and both lead to trifling 

 courses of reflection, in which the mind acquiesces, and is thus 

 diverted from more important subjects. But physicians exercise 

 a much more useful labour in the consideration of the secondary 

 qualities of things, and the operations of attraction, repulsion, 

 attenuation, inspissation, dilatation, astringency, separation, 

 maturation, and the like ; and would do still more if they would 

 not corrupt these proper observations by the two systems I have 

 alluded to, of elementary qualities and specific powers, by which 

 they either reduce the secondary to first qualities, and their 

 subtile and immeasurable composition, or at any rate neglect to 

 advance by greater and more diligent observation to the third 

 and fourth qualities, thus terminating their contemplation pre 

 maturely. Nor are these powers (or the like) to be investigated 

 only among the medicines for the human body, but also in all 

 changes of other natural bodies. 



A greater evil arises from the contemplation and investigation 

 rather of the stationary principles of things from which, than of 

 the active by which things themselves are created. For the 

 former only serve for discussion, the latter for practice. Nor is 

 any value to be set on those common differences of motion 

 which are observed in the received system of natural philosophy, 

 as generation, corruption, augmentation, diminution, alteration, 

 and translation. For this is their meaning: if a body, unchanged 

 in other respects, is moved from its place, this is translation ; it 

 the place and species be given, but the quantity changed, it is 

 alteration ; but, if from such a change, the mass and quantity of 

 the body do not continue the same, this is the motion of augmen 

 tation and diminution ; if the change be continued so as to vary 

 the species and substance, and transfuse them to others, this is 

 generation and corruption. All this is merely popular, and by 

 no means penetrates into nature ; and these are but the measures 

 and bounds of motion, and not different species of it j they 

 merely suggest how far, and not how or whence. For they ex 

 hibit neither the affections of bodies nor the process of their 

 parts, but merely establish a division of that motion, which 

 coarsely exhibits to the senses matter in its varied form. Even 

 when they wish to point out something relative to the causes of 

 motion, and to establish a division of them, they most absurdly 



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