Page:Popular Science Monthly Volume 79.djvu/472

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were discontinuous, if between any two beings an intermediate type were logically capable of existing, but actually non-existent, the universe would stand convicted of irrationality. A thing for the existence of which there was just as much "reason" as there was for the existence of certain other things would have failed of realization, while the others arbitrarily enjoyed the privilege of actuality. The principle of continuity owed its vogue in part, also, to the influence of the Leibnitian calculus, which had brought infinitesimals and the notion of the continuum peculiarly into fashion.

Applied primarily to the "monads" of Leibniz's metaphysics, the principle found a multitude of other applications. It served, for example, as the chief basis of the arguments for optimism of which the early eighteenth century was so fond. Pope's "Essay on Man" is full of the argument from the necessity of continuity to the necessity of imperfections and apparent evils.

Vast chain of being! which from God began;
Nature's ethereal, human, angel, man,
Beast, bird, fish, insect, whom no eye can see,
No glass can reach; from infinite to thee,
From thee to nothing. On superior powers
Were we to press, inferior might on ours;
Or in the full creation leave a void,
Where, one step broken, the great scale's destroyed.

For the limitations of man's lot the sufficient consolation is that the principle of continuity requires them; in a system

Where all must full or not coherent be,
And all that rises, rise in due degree,—
Then in the scale of reasoning life 'tis plain
There must be, somewhere, such a rank as man.

From the assumption of the same principle sprang the inquiries from which the science of anthropology may be said eventually to have originated. As a historian of the beginnings of that science has said:

The question concerning the line of demarcation between man and the animal kingdom was plainly forced upon anthropology by the philosophy of Leibniz. The lex continui demanded the discovery of that "grade" (nuance) of existence among the higher organisms which comes nearest to the human species. And so there began the celebrated quest of the "missing link." In the first phase of this quest, the missing link was sought at the lower limits of humanity itself. It was held to be not impossible that among some of the more remote peoples semi-human beings might be found, such as had now and then been described in travelers' tales. Some voyagers had testified to having seen with their own eyes men with tails; others had encountered tribes incapable of speech. Linnæus mentions a homo troglodytes concerning whom it was not established with certainty whether he was more nearly related to the pygmies or to the orang-outang. The most eminent men of science down to a late period in the eighteenth century hesitated to reject absolutely the possibility of the existence of such beings.[1]
  1. Günther, "Die Wissenschaft vom Menschen im 18ten Jahrhundert," p. 30.