FUNDAMENTAL CONCEPTIONS 363 



an intellectual one in which the testimony of the senses plays only 

 an indirect part. 



The more recent developments in all physical science illustrate 

 this tendency to extend the field of knowledge beyond that which 

 can be directly apprehended by sense-perception. This kind of inves- 

 tigation undoubtedly results in a peculiar intellectual satisfaction; 

 it extends indefinitely the territorial domain of the mind; and it 

 arouses the consciousness that man possesses intellectual powers of 

 a capacity to learn the things of the external world to which no one 

 can set definite limits. 



An increasingly troublesome feature of astronomical research is 

 found in the unwieldy nature of some of the problems which it pre- 

 sents. The work of developing and applying the theory of a single 

 planet is very great in itself; but the nature of the problem now 

 requires for it its sufficient treatment that the entire family of eight 

 major planets shall be considered together. The full mathematical 

 development of the lunar theory could scarcely be compassed in the 

 professional life of one astronomer. It is still more difficult to see 

 how the problem of structure and motion in the stellar universe is to 

 be effectively handled in the future without systematic organization 

 of the forces concerned and without controlled division of labor. 

 These facts appear to suggest that the science of astronomy differs 

 somewhat from the generality of other branches of exact science in 

 this respect : that in working out some of its single and really integral 

 problems an unusually extensive combination of effort is required 

 in order to arrive at the result. This detracts from the personal glory 

 of the individual who is often able to investigate only one section of 

 an essentially integral' problem. But this fact does not appear to 

 deter the investigator in all cases, nor to lessen his enthusiasm. 



The single investigator in astronomy is not permitted to devise and 

 select crucial experiments (perhaps only one) by means of which an 

 hypothesis can be sustained, or overthrown, at once. Any astro- 

 nomical hypothesis which is at all of a fundamental character must 

 usually be discussed through induction from a great multitude of 

 observed facts, provided by numerous observers, in relation to whom 

 the relative value of their testimony must of itself be partly a matter 

 of induction. 



It may be worth while to consider for a moment the nature of the 

 scientific truth which the astronomer endeavors to ascertain. There 

 seems to be no occasion to enter upon a philosophical disquisition 

 concerning the real essence of truth and the possibility of objective 

 reality. The astronomer proceeds exactly as if the objective world 

 were real ; but he recognizes that the truths which he is able to ascer- 

 tain concerning it are of a relative character. What appears to be 

 most feasible and fruitful in astronomical research is the attempt to 



