PRESIDENTS ADDRESS—SECTION A. By 
that which constitutes us intelligent beings. The elements of 
the nexus between particular phenomena may often, and indeed 
generally do, imply the intermediation either of other actual 
phenomena, or of phenomena which might be realised as 
actual, had we other instruments or other sense-organs through 
which they could be made apparent. Ultimately, however, we 
invariably reach a region in which phenomena are conceived to 
he, not only beyond the range of sense-perception with our pre- 
sent natural endowment, not only beyond that, too, which has 
been opened up through our ingenuity in extending our natural 
powers by mechanical aids, but also beyond all possibility of 
actual sense-presentation. For example, no one anticipates that 
we shall ever directly see even atomic forms as built up into a 
molecule; much less is it expected that we shall see those 
elements by which they are conceived to be controlled and main- 
tained in definite mutual relations. 
But, further, even when we conceptually bridge the gap 
between phznomena, sensuously perceived, by others imagined 
as intermediate, this process—assumed ultimately to end—gives 
as a final result two phenomena in succession, supposed to be, 
as it were, immediately in the chain of causality; the one as 
antecedent, the other as consequent. 
37. Matter and Energy, and the Last Link in the Chain of 
Causality.—F or the purposes of natural science the two entities, 
in terms of which the explanation of the entire realm of Nature 
is proposed to be resolved, and which must appear in this last 
link in the chain of causality, are matter and energy, the latter 
being measured by the quantity and rate of motion of the former 
with reference to some point conceived as fixed; that is, by 
spatial and temporal elements (d). In other words, the pro- 
blem proposed really is, to reduce the phenomena to questions of 
mechanics by way of explaining their relations. 
38. Mass Implicitly Assumed as an Ultimate Property of 
Matter—Now, in mechanical conceptions and problems, since 
by its very definition energy is derivative, mass is implicitly 
assumed as an ultimate property of matter, and the motzon of 
matter as an ultimate phenomenon, behind either of which there 
is no occasion to, neither can we for the purpose of the explana- 
tion, go. 
39. The Conception of Energy Otherwise Unmeaning.—l, 
however, mass be regarded as a property of matter, to be de- 
duced from some other property of a more general character, 
then the conception of energy in its original form is no longer 
(d) Thus the kinetic energy of a particle is said to be } mu2 where m is its mass, and u 
its velocity in reference to some fixed point in its line of motion. Similarly, the kinetic 
energy of a system of such particles is 5 4 muz, The term energy is relative, a moving 
mass has energy only in relation to something else taken as fixed, because it has velocity 
only in that sense. 
