428 ELEMENTS OF BIOLOGY 



vance new facts from the theory, then it becomes a vaUd principle 

 or law. On the basis of such laws it is possible to deduce events that 

 may happen in the future, as the astronomer accurately predicts 

 an eclipse of the sun, or to describe the characteristics of chemical 

 elements as yet undiscovered, as the chemist has done, or to predict 

 with accuracy the inheritable characters that will appear in the prog- 

 eny of animals or plants, as is done by the geneticist. Thus science 

 employs inductive logic in formulating theories and deductive logic 

 in applying them. One of the attributes of the human mind is its 

 constant striving to interpret the universe and all it contains in 

 terms of laws, or regularities; it always has been so and no doubt 

 always will be so. Hence the scientific attitude is not new; in fact, 

 it is as old as human curiosity. 



The task of the biological sciences is, in terms of the analogy of 

 the Mexican jumping bean given at the beginning, the discovering 

 of the causes of the motions of the bean, which, having been solved, 

 involves the question of the causes of the motion of the insect 

 larva within. In turn, the solution of the problem of the motion of 

 the larva opens the question as to why the larval muscles contract. 

 Thus the pursuit of a problem comes to involve more and more 

 recondite studies. In the search for the ultimate why the scientist 

 employs the most intimate facts of Nature. She is called upon to 

 explain herself. Nothing is taken for granted, no facts are assumed 

 a priori, and all theories are held tentatively, ready to be discarded 

 if new facts invalidate them. It is so with such a well-established 

 doctrine as evolution, for instance; the facts at hand can only be 

 interpreted in the terms of this concept, but if in the future new 

 facts appear that are not in alignment with this interpretation, evo- 

 lution as a valid doctrine will be discarded. 



In the search for answers to the constantly appearing series of 

 questions and problems, sooner or later barriers are encountered; 

 so Science is always engaged in a struggle at the barriers between 

 what is known and what is knowable but as yet unknown. Thus 



