Inquiry into the Nature and Properties of the Blood. 205 



ideas of that subject are but very obscure and indistinct; but 

 how that HI process of time and by dihgent study, these ideas 

 may be rendered more distmct and clear, by means of the cre- 

 neral experience we may have at length acquired : for as we 

 observed above, it takes a long time for man to become ra- 

 tional ; or in other words, for the rational faculty of man to 

 become stored with those truths which are indispensable to his 

 becoming a truly rational or intelligent beino-. 



We canuot help bringing to your notice the connexion, com- 

 munion, and mutual respect existing between all things of the 

 world and nature;— for does not one science meet and^'enlaro-e 

 our apprehension of another, and every new acquisition afford 

 an explanation to what preceded ? By many and various facts 

 judiciously associated and mutually compared, our ideas are 

 illustrated and our reason illuminated ; for it is only by de- 

 grees that the mind disperses the shadows and clouds of 

 Ignorance and prejudice, and emerges thence into Ijo-ht. 

 Still, however, there is a danger of our relying upon our 

 thorough knowledge or experience of some single subject as 

 a means of our extending our reasoning to other things with 

 which It may have only a remote connexion. Examples of this 

 are too abundant in our own day : for how many are there 

 who are well skilled in one particular science, and who would 

 investigate or measure every other, by it alone. Thus the che- 

 mist may look for nothing but chemical affinities and decom- 

 positions in the three kingdoms of nature; the mathematician 

 lor nothmg but gravitating tendency, polarity, centripetal and 

 centrifugal forces ; the anatomist, for nothing but structure and 

 form; the painter, for nothing but colour, light and shade- the 

 musician, for nothing but harmony and sound ; and the physi- 

 cian, for nothing but irritability, and numerous other techni- 

 calities. Drawing general conclusions from such confined 

 sources, how dexterously does such limited experience favour 

 the mind in all its reveries, and how obstinately does it withstand 

 the objections advanced by the truly rational antagonists The 

 reason of this is, because no fact can exist which may not be 

 placed in some part or other of different series of ratiocina- 

 tions; just as one syllable, word, or phrase, may enter into and 

 torm a part of innumerable sentences and discourses ; one 

 Idea of innumerable series of thoughts, and one colour of in- 

 numerable pictures. One thing may always be inserted on 

 another, as branches are by the gardener; and thus a false 

 uifcrena- may be grafted on a certain fact, as a wild fVuit-tree 

 on the legitimate growth of the orchard. 



To avoid, therefore, being made the dupes of appearances, 

 we should never yield our assent to any theory, without its 

 having the concurrence of common or general experience; or 



unless 



