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parallel in each science, is what we understand by the term 

 form, adopting that word because it has grown into common 

 use, and is of familiar occurrence. 



3. He who has learnt the cause of a particular nature (such 

 as whiteness or heat), in particular subjects only, has acquired 

 but an imperfect knowledge: as he who can induce a certain 

 effect upon particular substances only, among those which are 

 susceptible of it, has acquired but an imperfect power. But he 

 who has only learnt the efficient and material cause (which 

 causes are variable and mere vehicles conveying form to particu- 

 lar substances) may perhaps arrive at some new discoveries in 

 matters of a similar nature, and prepared for the purpose, but 

 does not stir the limits of things which are much more deeply 

 rooted : whilst he who is acquainted with forms, comprehends 

 the unity of nature in substances apparently moit distinct from 

 each other. He can disclose and bring forwarc therefore, 

 (though it has never yet been done) things which n ''her the 

 vicissitudes of nature, nor the industry of experiment nor 

 chance itself, would ever have brought about, and which we aid 

 forever have escaped man's thoughts; from the discovery of 

 forms, therefore, results genuine theory and free practice. 



4. Although there is a most intimate connection, and almost 

 an identity between the ways of human power and human 

 knowledge, yet, on account of the pernicious and inveterate habit 

 of dwelling upon abstractions, it is by far the safest method to 

 commence and build up the sciences from those foundations 

 which bear a relation to the practical division, and to let them 

 mark out and limit the theoretical. We must consider, there- 

 fore, what precepts, or what direction or guide, a person would 

 most desire, in order to generate and superinduce any nature 

 upon a given body : and this not in abstruse, but in the plainest 

 language. 



For instance, if a person should wish to superinduce the yel- 

 low color of gold upon silver, or an additional weight (observ- 

 ing always the laws of matter) or transparency on an opaque 

 stone, or tenacity in glass, or vegetation on a substance which 

 is not vegetable, we must (I say) consider what species of pre- 

 cept or guide this person would prefer. And firstly, he will 

 doubtless be anxious to be shown some method that will neither 

 fail in effect, nor deceive him in the trial of it ; secondly, he 

 will be anxious that the prescribed method should not restrict 

 him and tie him down to peculiar means, and certain particular 

 methods of acting; for he will, perhaps, be at loss, and without 

 the power or opportunity of collecting and procuring such 

 means. Now if there be other means and methods (besides 

 those prescribed) of creating such a nature, they will perhaps 

 be of such a kind as are in his power, yet by the confined limits 

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