50 SPOLIA ZEYLANICA. 
on investigation were found to exist. The observation of a 
certain dark line in the sun’s spectrum led Sir Norman (then 
Mr.) Lockyer to predict the existence of a new element in the 
sun’s atmosphere; many years later another investigator 
discovered that element (helium) on earth. These are among 
the classical examples of scientific deduction. 
First, it must be recollected that a wrong theory is often 
capable of extended application, and predicted consequences of 
that theory may be found to coincide with experience. The 
theory of diminishing ancestral contributions is as old as the 
human race itself, and has worked so well that no one thought 
it necessary to call attention to the theory at all till the 
twentieth century. It is now held by competent authorities 
to be totally inadequate. Again, predictions were based on 
Newton’s corpuscular theory of light, and the truth of the 
theory was held to be proved when these predictions were 
verified. Nowadays the corpuscular theory is only of 
historical interest. 
There can be no kind of a question, of course, that the more 
we investigate and theorize about Nature the more utilitarian 
do our theories become, and the larger grows the field of fact 
which they are capable of explaining. 
In a word, the truer do they become from our own stand- 
point. Thus, a theory is true in proportion as it is applicable. 
So that if we say that the electro-magnetic theory of light is 
the true interpretation of certain manifestations, all we can 
logically mean is that it is the most capable and comprehensive 
guess at the mechanism of those manifestations which has, up 
to the present, been put forward. Whether there is or is not 
anything behind visible Nature corresponding to our concep- 
tion of ether waves is quite another question, and one to 
which we cannot possibly give an absolutely definite answer. 
We may think there is, or we may think there is not ; or, again, 
we may express a philosophical doubt about it. At the best 
we can only guess at the mechanism of Nature : we can never 
look into Nature and see its works. 
It might be difficult to prove that there is anything behind 
phenomena at all, but there is surely a very strong presumption 
that there is something there ; indeed, in the absence cf evidence 
