has ever written is its practical refutation—is too obvious, almost, to require pointing out.
While the example just discussed was a case of absolute inconceivability, the other instances given by Mill are cases of true relative inconceivability. The first is that of antipodes which were long held to be impossible, and are now not only readily conceived as possible, but known to be real. This is true enough, but it finds its explanation, not in the law of inseparable association to which it is referred by Mill, but in the fact that our ancestors held an erroneous concept of the action of gravity. They supposed that the direction in which gravity acted was an absolute direction in space; they did not realize that it was a direction toward the earth's centre of gravity; downward to them meant something very different from the sense we attach to that word. With this erroneous concept they could not reconcile the fact that the force of gravity held our antipodes in position as well as ourselves; nor can we. But we have a juster concept of gravity, and the mode and direction of its action; the spurious notion with which the notion of antipodes was inconsistent, has been removed, and the inconceivability of antipodes is at an end.
Similar observations apply to Mill's remaining example (which is to us the most interesting, and that for the sake of which I have carried the discussion of this dry subject to this length) of the inconceivability of actio in distans, to which I have already alluded. The true source of our inability to conceive actio in distans is, I trust, now apparent. This inability results from the inconsistency of this concept with the prevailing concepts respecting material presence. If we reverse the proposition, that a body acts where it is, and say that a body is where it acts, the inconceivability disappears at once. One of the wisest utterances ever made on this subject is the saying of Thomas Carlyle (quoted by Mill himself in his "System of Logic," in another connection): "You say a body cannot act where it is not? With all my heart; but, pray, where is it?" Of course, a reconstitution of our concepts of material presence, in the sense here indicated, would be in utter conflict with the theory of the mechanical construction of matter from elements which are absolutely limited, hard, unchangeable, and separated from each other by absolutely void spaces. It is significant that nearly all the efficient laborers in the quarries of physical science vaguely feel, if they do not distinctly see, that such a reconstitution is necessary. Such a feeling was at the bottom of Faraday's attempt to construct matter out of the convergence and intersection of mere lines of force, so as to secure to each point of intersection (or, in the language of Faraday, to each centre of force) a virtual omnipresence, the extent of the lines of force being infinite.
I may be permitted to say, at the end of this long but unavoidable excursion into the regions of logic and psychology, that the doctrine, according: to which there is no warrant for the deliverances of our