504 EDUCATION 



But every astronomer is also a mathematician and physicist, and it 

 is the application of mathematical and physical laws to astronomy 

 that has given to this science all its intellectual splendour that 

 has converted the astrologer into the astronomer, that has linked 

 together the facts of astronomy in chains of causation, that 

 has made it in great measure a deductive science founded on 

 laws. 



822. Chemistry is based on an enormous number of facts, but, 

 as far as I am aware, has only one law of considerable importance, 

 Dalton's Atomic Theory, which is usually regarded by chemists 

 as their most valuable possession. 



823. Systematic zoology, botany, anatomy, and the other 

 systematic sciences that relate to living beings are also founded 

 on a great number of facts, probably on a greater number of 

 recorded and described facts than any of the other sciences. But 

 they have no laws. They are descriptive not interpretative ; their 

 facts are classified according to co-existences and resemblances, 

 not in chains of causation. In effect, they consist of a multi- 

 tude of definitions. Thus a systematic zoologist will tell us no 

 more about a man than that he possesses certain characters, and 

 that therefore he is an animal belonging to the sub-kingdom 

 Vertebrata, class Mammalia, order Bimana, and so forth. The 

 faculties required by the young learner in these sciences are 

 mainly observation and recollection. No doubt, a great deal of 

 thought comparison, discrimination, association, and the like 

 is needed also ; but, as compared to the amount required in 

 physics and mathematics, it is very small in proportion to the 

 number of facts. Moreover, it is not the same kind of thought 

 not deductive, not interpretative thought, not thought about the 

 sequences of phenomena, not a linking together of facts in the 

 relation of cause and effect, not a process of inferring the pre- 

 viously unknown as a necessary consequence from the previously 

 known, not ratiocination. 



824. If a student has exceptional powers of recollection and 

 observation he may become an exceptionally good systematist. 

 But no such powers by themselves will enable him to become 

 a great mathematician or astronomer. The difference between 

 the interpretative and descriptive sciences is vividly illustrated 

 by the circumstance that I am able in a short time to ascertain 

 all that I want to know, indeed all that is known to the average 

 systematist, about any animal or plant, by turning to the books 

 on my shelves; whereas no number of books will enable me to 



