142 
As Lewis says that “ the idea of spirit, as separate from 
matter, is imaginary.”* Or may it not be the shadow of some- 
thing, “ the suggestive aspect of something,” as others 
appear to say ? Or may it not be beyond our power to con- 
ceive of mind as a substance, as Professor Allman says “ the 
power of conceiving of a substance different from that of 
matter is beyond the limits of human intelligence ? ” f 
Substance means that in which properties and attributes 
inhere. Attributes and properties imply a substance of which 
they are the manifestations. They cannot exist separate from 
substance. Fear must exist in some mind ; and colour must 
exist in some body. 
There are two substances in nature, — matter, of which the 
human brain forms a part ; and spirit, of which the human mind 
forms a part. And we have as clear ideas of mind as we have 
of brain, the essence of each being equally unknown to us. 
“ Sensation convinces us that there are extended substances, 
and reflection that there are thinking ones. We perceive not 
the nature of extension clearer than we do of thinking.” J 
The attributes and properties of one substance cannot be 
transferred to another. The attributes, properties, and 
qualities of mind cannot be predicated of material brain 
atoms ; and the attributes, properties, and qualities of brain 
atoms cannot be predicated of mind. 
“ Anger and fear are qualities incapable of being exhibited 
as functions of brain matter ” § ; and, on the other hand, 
extension, resistance, gravity, colour, are terms incapable of 
application to mind. 
Tyndall, however, ascribes to brain matter what philoso- 
phers ascribe to mind. He affirms the idea of self-deter- 
mining as the attribute of a molecule. He says, “ given the 
state of the brain, and the corresponding thought might be 
inferred. Or given the thought, and the state of the brain 
might be inferred.” || But he admits that this is all mere 
assumption when he says, “ molecular groupings and mole- 
cular motions explain nothing.”^ 
Not One Entity . 
May not mind and brain be one entity, with two aspects, 
a unity with two faces ; or may not the one be the substratum, 
and the other the aspect of it ? 
* Problems, 430. t Sheffield Address. $ Stewart’s Hiss., 112. 
§ North British Review, vol. liii., p. 125. 
| Victoria Institute, vol. vii., p. 137. IF Ibid., p. 141. 
