PRIMARY CONCEPTS OF MODERN SCIENCE. 223 



is no absolute residuum which is exempt from all change and remains 

 constant amid all variation — when the relation of primordial matter to 

 its structural, or rather formative, agencies is properly understood — 

 the whole science of molecular statics and dynamics will press at once 

 for thorough reorganization. 



It may be proper, in this connection, before I proceed to the dis- 

 cussion of another topic, to say a few words about the ordinary me- 

 chanical explanation of the molecular states of matter, or states of 

 aggregation, on the basis of the atomic theory. This explanation pro- 

 ceeds on the assumption that the molecular states are produced by the 

 conflict of antagonistic central forces — molecular attraction and repul- 

 sion — the preponderance of the one or the other of which gives rise to 

 the solid and gaseous forms, while their balance or equilibrium results 

 in the liquid state. The utter futility of this explanation is apparent 

 at a glance. Even waiving the considerations presented by Herbert 

 Spencer (" First Principles," p. 60, et seq.) that, in view of the necessary 

 variation of the attractive and repulsive forces in the inverse ratio of 

 the squares of the distances, the constituent atoms of a body, if they 

 are in equilibrio at any particular distance, must be equally in equilibrio 

 at all other distances, and that their density or state, therefore, must 

 be invariable ; and, admitting that the increase or diminution of the 

 repulsive force, heat, may render the preponderance of either force, 

 and thus the change of density or state of aggregation, possible : what 

 becomes of the liquid state as corresponding to the exact balance of 

 these two forces in the absence of external coercion ? The exact bal- 

 ance of the two opposing forces is a mere mathematical limit which 

 must be passed with the slightest preponderance of either force over 

 the other. All bodies being subject to continual changes of tempera- 

 ture, the equilibrium can at best be but momentary ; it must of neces- 

 sity be of the most labile kind. If the mechanical explanation of the 

 molecular states were valid, all bodies would present the phenomena 

 exhibited by arsenic under the action of heat — they would at once pass 

 from the solid into the gaseous form, the intervening liquid state van- 

 ishing after the manner of all limits. 



The notion of the essential solidity of matter of necessity leads to — 

 indeed, at bottom, is identical with — the assumption of its absolute 

 hardness or unchangeability of volume, and thus involves the theory 

 of the atomic constitution of matter in its ordinary form. This as- 

 sumption is connected with another fallacious bias of the mind, which 

 results from the inability of the mind to consider phenomena other- 

 wise than singly, and under some one definite aspect — the tendency to 

 assign absolute limits to every series of material phenomena. It has 

 been a favorite tenet, not only of metaphysicians but of physicists as 

 well, that reality is cognizable only as absolute, permanent, and inva- 

 riable, or, as the metaphysicians of the sixteenth and seventeenth cen- 

 turies expressed it, sub specie ceterni et absoluti. This proposition, like 



