180 SECTIONAL ADDRESSES 
I interpret the similar phenomena, on analogy with my immediate 
(non-sensorial) experience of self-identity, and posit a selfsame physical 
book enduring intime. Finally, my notion of unity also is derived from 
the same source of immédiate, non-sensorial experience of myself, and 
analogically applied to sensed-things and thought-things alike. 
ORIGIN OF SCIENTIFIC CONCEPTS: ENERGY. 
Passing next to the explanatory concept of energy, still in general use 
in the sciences of Nature, we find that this also is not to be discovered 
among the particular selected sensory phenomena with which they deal. 
This concept of physical energy, kinetic and potential, refers to a postu- 
lated persistent entity (‘ same thing ’), constant in amount, which may be 
transformed from one state to another, and is capable of doing work in 
bringing about physical movements. To what source in experience can 
we trace this notion? Clearly it is not sensorially apprehended in the 
physical phenomena observed. It might at first sight seem that it should 
be traced to kinzsthetic experience, or the sense of effort in bodily 
activity by which different kinds of work are done ; that we read this 
analogically into the physical phenomena, and project the result into a 
‘ physical’ world. But I do not think that this can be a true explanation, 
for the reason that, like the properties of the book just considered, the 
sense of effort, experienced in one case, is only similar to the sense of 
effort experienced in another. It can in no sensory way be shown that 
they are identical. Likewise, the body, in the same way as the book, in 
any successive pulses of sensorial apprehension, displays no more than a 
relation of likeness. Accordingly, I appeal again to my immediate non- 
sensorial experience of self-identity, in which I discover an active self 
energising in one way or another. It is true I do not find any perpetual 
and unbroken continuity of self-consciousness ; but, whenever I am 
conscious, notwithstanding all the changes that take place in the pheno- 
menal world, including those of my own body, I am conscious of the same 
unitary and self-identical I. Now, can we find the basis of the concept 
of energy here? I maintain that we can, in the sense that this self does 
actualise, or energise, in different ways, now perceiving, now judging, 
now resolving, now enjoying, and the like. And from this I infer, though 
the inference is by no means a remote one, that a self which does all 
these things can do any one of them, even if it is not actually doing that 
one at the moment. Here I find, in immediate living experience, the 
source from which the abstract concepts of energy and dynamism are 
drawn ; and these concepts, applied to the phenomena of motion or change, 
become those of kinetic and potential energy, and are projected upon an 
extra-mental world of things which we have conceived on analogy with 
ourselves. 
VALIDITY OF SCIENTIFIC CONCEPTS. 
There are no doubt other lines of approach to the development of the 
thesis I am maintaining than the one I have taken ; but I have chosen this _ 
because it most readily allows me to stress the point I wish to make. If 
we begin with the principles and postulates of which the different sciences 
