The inference, such as it is, depends on the Law of excluded middle.
The law of excluded middle: 'Everything must either be or not be.'
The absolute fact comes under the Law of excluded middle, but a personal opinion is not an absolute fact.
In this determinate nature lies the worth of the excluded middle.
These rules are very far from being self-evident, any more than the maxims of Contradiction and of the excluded middle.
If there is a mean, the conditioned, and the two extremes, then "excluded middle" has nothing to do with the matter at all.
Hence the principle of excluded middle does not hold good of mere contrary terms.
From this law of thought follows directly the third, viz., the Principle of the excluded middle.
With these three intellectual laws of identity, of contradiction, and of the excluded middle, formal logic begins.
Take, for example, the law of excluded middle in the form ‘all propositions are true or false.’