602 



Mr. ELLIS, ON THE THEORY OF MATTER. 



of colour corresponds and is due to a difference between the essential constitution of the two 

 substances. Now the essential constitution here spoken of, and consequently the differences which 

 individuate it in different cases, may conceivably be something altogether incognisable to the human 

 intellect. The notion that it is so was expressed scholastically by saying that substantial forms are 

 not cognoscible. But if, setting aside this opinion, we affirm that the essential constitution of 

 each substance is a matter of which the mind can take cognisance, we are led at once to the 

 distinction between primary and secondary qualities. The first are ascribed to each substance as 

 its essential attributes, in virtue of which it is that which it is — the second result from the primary*, 

 (by which as we have said the essential or formal constitution of the substance in question is deter- 

 mined,) and have reference to the mind by which they are perceived, while the primary are ascribed 

 to it independently of any reference to a percipient mind : and a distinction, analogous or identical 

 with that between primary and secondary qualities, has accordingly been expressed by the anti- 

 thesis between that which is a parte hominis and that which is a parte universi. That the 

 distinction between primary and secondary qualities is necessary on the hypothesis on which we are 

 proceeding, appears at once from the consideration that if we affirm that all the qualities of bodies 

 of which we can form any conception are equally subjective and phenomenal, nothing will remain 

 of which the mind can take cognisance, and by means of which our conception of the nature of any 

 one substance can be discriminated from that of any other-f. Let it be granted therefore that the 

 distinction of primary and secondary qualities is a necessary element of physical science. It follows 

 from this that the secondary qualities in a manner disappear when we look at the universe from the 

 scientific point of view. Instead of colours we have vibrations of the luminiferous ether — instead 

 of sounds vibrations of the ambient air, and so on. Now from hence it follows that all the 

 phenomena which we see produced, of whatever nature they may be, are all in reality dependent on 

 the primary qualities of matter. Furthermore, these primary qualities themselves all involve the 

 idea of motion or of a tendency to motion. A body changes its form in virtue of the local motion 

 (absolute or relative) of some of its parts ; and when 1 press a stone between my hands, I find that 

 I can produce no sensible change of form, while contrariwise the stone reacts against my hands, 

 tending to make them move in opposite directions. I then say that the stone is hard as a mode of 

 expressing this, viz. that when an attempt is made to produce relative local motion of its parts, it 

 resists it in virtue of its reactive tendency to produce motion in that which acts upon it. Again, 

 a body whose parts are readily susceptible of relative local motion is said to be soft or fluid, and 

 when a sensible change of form is accompanied by a tendency to such motion as shall restore the 

 original form, it is said to be elastic, and so on. We thus arrive at a point of view at which all 

 secondary qualities having disappeared, and all primary ones J having been resolved into motion 

 and tendency to motion, the sciences which relate to phenomena appear to be resolved into the 

 general doctrine of motion. But if this be true the universe can it is said present to us nothing 

 but one great dynamical problem. Motion, and force the cause of motion, belong essentially to the 

 domain of mechanics : and if chemical affinity be a cause of local motion, that is, if in virtue of its 

 action || a particle of matter finds itself at a given time in a position different from that which it 

 would else have occupied, chemical affinity is not really distinct from mechanical force (whicli 

 looked at from the dynamical point of view includes everything which is a cause of motion) ; 

 whereas if it be not a cause of motion the enquiry at once presents itself of what is it ? In illus- 

 tration of this view we may refer to any chemical experiment. If an acid is dropped into a glass 

 containing any vegetable blue, the colour is changed to red. But to say this is to say that the 



• Or that which in its formation it was to be, to ti t)i/ 



elvai. 



I The doctrine of the cognoscibility of substantial forms, 

 which is intimately connected with this distinction, is as Leibnitz 

 in ettect remarks, as it were the common character of those who 



with more or less success attempted in the seventeenth century, 

 the restoration of science. Vid. Leibnitz, Epist. ad Thomas, I. 



X That is, all that are commonly enumerated as primary 

 qualities. 



II As, for instance, in the phenomenon of crystallization. 



