Ix LIMITS OF NATURAL SELECTION IN MAN 207 
adopts the “well founded doctrine that life is the cause and 
not the consequence of organisation.” In his celebrated 
article “On the Physical Basis of Life,” however, he maintains 
that life is a property of protoplasm, and that protoplasm 
owes its properties to the nature and disposition of its 
molecules. Hence he terms it “the matter of life,” and 
believes that all the physical properties of organised beings 
are due to the physical properties of protoplasm. So far we 
might, perhaps, follow him, but he does not stop here. He 
proceeds to bridge over that chasm which Professor Tyndall 
has declared to be “intellectually impassable,” and, by means 
which he states to be logical, arrives at the conclusion that 
our “thoughis are the expression of molecular changes in that 
matter of life which is the source of our other vital phenomena.” 
Not having been able to find any clue in Professor Huxley’s 
writings to the steps by which he passes from those vital 
phenomena, which consists only, in their last analysis, of 
movements of particles of matter, to those other phenomena 
which we term thought, sensation, or consciousness, but 
knowing that so positive an expression of opinion from him 
will have great weight with many persons, I shall endeavour 
to show, with as much brevity as is compatible with clearness, 
that this theory is not only incapable of proof, but is also, as 
it appears to me, inconsistent with accurate conceptions of 
molecular physics. To do this, and in order further to 
develop my views, I shall have to give a brief sketch of the 
most recent speculations and discoveries as to the ultimate 
nature and constitution of matter. 
The Nature of Matter 
It has been long seen by the deepest thinkers on the 
subject, that atoms,—considered as minute solid bodies from 
which emanate the attractive and repulsive forces which give 
what we term matter its properties,—could serve no purpose 
whatever ; since it is universally admitted that the supposed 
atoms never touch each other, and it cannot be conceived that 
these homogeneous, indivisible, solid units are themselves the 
ultimate cause of the forces that emanate from their centres. 
As, therefore, none of the properties of matter can be due to 
the atoms themselves, but only to the forces which emanate 
