224 THE POPULAR SCIENCE MONTHLY. 



so many others which have served as pillars of imposing metaphysical 

 structures, is the precise opposite of the truth. All material reality is, 

 in its nature, not absolute, but essentially relative. All material re- 

 ality depends upon determination ; and determination is essentially 

 limitation, as even Spinoza well knew. A " thing in and by itself " is 

 an impossibility. And I may add here (without dwelling upon it fur- 

 ther, a discussion of this subject being foreign to my theme), the 

 " thing per se " is not only impossible, according to the criteria of our 

 intellect, but it is not the object of knowledge, in any sense, and can- 

 not, therefore, be the legitimate subject of speculation. As Ferrier 

 would say, we can neither know it nor be ignorant of it. I do not 

 speak here merely of objects without relation to the intellect, in the 

 sense of Ferrier's " Theory of Ignorance," but of objects without rela- 

 tion to each other. "We only know anything," justly says John 

 Stuart Mill (" Examination of Sir W. Hamilton's Philosophy," i., 14), 

 " by knowing it as distinguished from something else ; all conscious- 

 ness is of difference ; two objects is the smallest number required to 

 constitute consciousness ; a thing is only seen to be what it is by con- 

 trast with what it is not." Here, again, the doctrines of psychology 

 are corroborated by the teachings of the science of language. " Words," 

 says Rev. Richard Garnett ("Philological Essays," p. 282), "express 

 the relations of things ; and this, it is believed, is strictly applicable to 

 every word in every language, and under every possible modification." 

 Among those who have had occasion of late to insist upon the 

 relativity of all objective reality is Prof. Helmholtz. Speaking of the 

 inveterate prejudice according to which the qualities of things must 

 be analogous to, or identical with, our perceptions of them, he says 

 (" Die neueren Fortschritte in der Theorie des Sehens," Pop. wiss. 

 Yortraege II., 55, et seq.) : " Every property or quality of a thing is in 

 reality nothing else than its capability of producing certain effects on 

 other things. The effect occurs either between connatural parts of the 

 same body, so as to produce differences of aggregation, or it proceeds 

 from one body to another, as in the case of chemical reactions ; or the 

 effects are upon our organs of sense and manifest themselves as sensa- 

 tions such as those with which we are here concerned (the sensations 

 of sight). Such an effect we call a ' property,' its reagent being un- 

 derstood without being expressly mentioned. Thus we speak of the 

 'solubility' of a substance, meaning its behavior toward water; we 

 speak of its c weight,' meaning its attraction to the earth ; and we 

 may justly call a substance ' blue,' under the tacit assumption that we 

 are only speaking of its action upon a normal eye. But, if what we 

 call a property always implies a relation between two things, then a 

 property or quality can never depend upon the nature of one agent 

 alone, but exists only in relation to and dependence on the nature of 

 some second object acted upon. Hence, there is really no sense in 

 talking of properties of light which belong to it absolutely, indepen- 



