14. PROCEEDINGS OF THE ROYAL SOCIETY OF QUEENSLAND, 
scheme is built up, but at no stage is any step made of 
necessity; rather is it, in Poineare’s words, “‘the product 
of unconscious opportunism. ”’ 
The final test of the adequacy of the scheme as a 
description of the physical universe is consistency. When 
we have shown this consistency we have a theory which 
is sufficient to account for the phenomena; to deduce the 
necessity of the theory we should have to prove the fact 
that no other consistent scheme could be evolved. Thus 
Science establishes the sufficiency but not the necessity of 
its description of Nature. The common tendency is, 
however, to treat the sufficient explanation as a necessary 
description and then to materialize the concepts embodied 
in it. 
We have seen that the revival of Science was accom- 
panied by a change of view as to its functions. The search 
for first causes gave place to an attempt to formulate 
ordered descriptions. There is need now to realize that 
these descriptions are not accurate word pictures, but 
merely schematic representations, probably much simph- 
fied, of underlying realities. As an example of the 
hindrance to the progress of Science which arises from the 
tendency to assume one particular solution of the meta- 
physical problem of reality, consider the history of the 
Theory of Relativity. 
In the last ten years Relativity has opened up a field 
of investigation which promises to be exceedingly fruitful. 
The experimental work from which the theory arises is 
over thirty years old, and the essential parts of the mathe- 
matical theory by which it is worked out have been in 
existence during the whole of that period. The delay of 
thirty years is due primarily to a failure to eriticise 
the metaphysical assumptions underlying the Michelson- 
Morley experiment. The theory of that experiment rested 
on three assumptions—the reality of the A‘ther, and the 
absolute meaning of the terms ‘‘leneth’’ and ‘‘period of 
duration’’ as applied to objects and events; the last two 
being practically equivalent to the assumptions of the 
reality and mutual independence of space and time. 
When the experiment failed in its object, the determina- 
tion of the velocity of the earth through the Atther, the 
scientific world turned its attention to explaining away the 
failure by modifying the properties of matter and ignored 
