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Mr. Moore. — Not a quality. The physicist I have referred to said to 
me, “ The ultimate atoms differ in quality only so far as shape and size go.” 
I asked him, “ Do you not admit colour to be an essential property ? ” but 
he replied, “ No, that is a sensation, an idea ” — calling colour a sensation. 
The Chairman. — At any rate, colour, as we know it, is simply an impres- 
sion upon the optic nerve communicated to the brain. 
Mr. Moore. — No. 
Mr. Brooke. — Oh, certainly yes. 
The Chairman. — The conception in the mind is the combined result of 
our sensations, and the external reality. We cannot say that the external 
reality is the same as our sensations ; there is a cause, external to my mind, 
which causes certain perceptions of it, but on my optic nerve. This is an 
unquestionable truth. I take up this piece of paper, it seems to me quite 
absurd to say that its colour, as I see it, is in the piece of paper, though I 
am quite ready to admit that there is something in the paper which causes 
the particular sensation, which is quite another question. But I understood 
Mr. Moore to say that colour is a positive quality in the external thing 
itself. 
Dr. Irons. — Perhaps I may be allowed to continue my catechising. I 
want to know whether forces proceed in right lines. How do they go ? Are 
they circular, or direct, or gyratory, or what ? Do they go straight on, and, if 
not, what gives them any other direction ? I am now assuming in my ques- 
tion that force can certainly do something. How does it do it ? And is 
there anything afterwards to modify it and give it shape ? 
The Chairman.- — I should like to ask Mr. Brooke a question before he 
replies. Will he undertake to discriminate between power, force, and energy, 
according to his own views ? 
Mr. Brooke. — In reply to the last question, I would say if you will define 
power, and what you mean by it, for I do not know what the definition is ? 
I will draw a distinction if I can. Until then I do not know what I am 
talking about. I have not defined power, though I have defined force and 
energy. With regard to the question put by Dr. Irons, as to the direction 
in which force goes, it is quite clear that I have defined force to be essentially 
either an attraction or a repulsion — that is to say, either a push or a pull— 
between two particles, whatever they may be, or masses or portions of matter. 
It is either a push or a pull. It cannot go anywhere ; it is an existence. You 
cannot talk of its “ going” in any direction. In reply to previous observations 
that have been made, I will first take Dr. M‘Cann, ’who objects to my 
strictures upon his view of causation, and says they are wholly defective ; 
because, to take the example he quotes — the case of a book falling to the 
ground — it is not the force of gravitation, but it is his will which causes it. 
Well, if that be so, suppose instead of willing that the book should go down 
on the floor, I willed that it should go up to the ceiling. Would that make 
it do so ? My will clearly is not the cause of its falling ; it no more descends 
than it ascends by my will. We have been told that there are certain people 
who profess to will that a book should go up to the ceiling, and that it does 
YOL. VII. S 
