Among the more startling, if not decidedly brilliant, vital theories which have been advanced within the last few years, is that which makes life an "undiscovered correlative of force." Those who have the reputation of being the profoundest thinkers and delvers in the newly-discovered realm of Force-correlation in Europe, and who have more or less modestly contributed to that reputation themselves, have evidently thought to eclipse, if not to entirely throw into the shade, the great exploit of Leverrier, in pointing out the exact place in their empirical heavens where the superior optics of some future observer shall behold, in all its glory, this "undiscovered correlative of force," which they have indicated as lying within the higher possibilities and potentialities of matter. Precisely what they mean by this undiscovered correlate, is what puzzles us quite as much to determine as it does the materialists to explain. Were they to define life as an "undiscovered force" simply, their definition would manifestly lack in brilliancy what it would conclusively make up in precision and accuracy of definitional statement. But such a poor metaphrastic and half-circular exposition of vital force would never answer the necessities of that profounder profundity required for the success of modern scientific treatises. Hence the interpolation of this "correlative" of theirs. Let us ascertain, if we can, what it means, since they are so chary of informing us themselves. A "correlate" of a thing--any thing--simply implies the reciprocal relation it bears to some other thing. As a cognate term it expresses nothing, can express nothing, but reciprocity of relationship, such as father to son, brother to sister, uncle to aunt, nephews to nieces, etc. As applied to vital force, it means nothing more nor less than that this particular force stands in some sort of relationship to the other forces of nature, or, as they would have us believe, the _material_ forces of nature. And the simple strength or potentiality of this relationship is what makes all the difference between the severally related forces of the universe, since it would be as impossible to differentiate a fixed relationship as to change the nature of vital units. But whether vital force, as a distinct correlate, is paternal or filial, brotherly or sisterly, avuncular or amital in its relationship, is not stated. The scientific formula, however, may be stated thus: As A (chemical force) is to B (molecular force) so is C (a third known force) to _x_ (the vital or unknown force); so that, by multiplying the antecedents and consequents together, and eliminating the value of _x_, we may mathematically obtain the value of vital force.