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 enough to start from true premises. In the syllogism it was supposed that such a form had been found. From all swans are white and this bird is a swan it was to follow inevitably that this bird is white, and the course of nature would eternally conform to the prophetic demonstrations of logic.

Yet logicians also had soon to note that even formally there was something wrong about this syllogistic form. It seemed to "prove" what was either nothing new or nothing known. To justify the "major premise" "all swans are white", must not its assertor have already seen this swan and know that it is white? Or, if he did not know this, is he not risking an assertion about some "swans" on the strength of what he knows about others? And what right had he thus to argue from the known to the unknown? Can an "inference" be "valid" if it involves a risk?

When therefore black swans arrive from Australia to upset his dogmatizing, what is he to do? Will he say his major premise was a definition, and no bird, however swan-like, shall be called a "swan" if it cannot pass his color-test? If so, his reasoning is still caught in the old dilemma, that he either "proves" nothing new or begs the question in another way. For he then had no right to assert his "minor premise", this bird is a swan, if he knew not it was white. Or will he, desperately, say "in both of these interpretations the syllogistic form is fatuous; but kindly understand it as asserting a law of nature which is immutable, and applied to the particular case in the minor premise." But, if so, how does he know that his "law" applies to the "case"? that the "case" is such as he takes it to be? that he has picked out the right "law" to deal