If we say _A man so precise in his walk and conversation is either a saint or a consummate hypocrite_; or, again, _One who is happy in a solitary life is either more or less than man_; we cannot in such cases mean that the subject may be both.

On the other hand, if it be said that _the author of 'A Tale of a Tub' is either a misanthrope or a dyspeptic_, the alternatives are not incompatible.

Or, again, given that _X.

is a lunatic, or a lover, or a poet_, the three predicates have much congruity.
It has been urged that in Logic, language should be made as exact and definite as possible, and that this requires the exclusive interpretation 'not both.' But it seems a better argument, that Logic (1) should be able to express all meanings, and (2), as the science of evidence, must not assume more than is given; to be on the safe side, it must in doubtful cases assume the least, just as it generally assumes a preindesignate term to be of particular quantity; and, therefore 'either, or' means 'one, or the other, or both.' However, when both the alternative propositions have the same subject, as _Either A is B, or A is C_, if the two predicates are contrary or contradictory terms (as 'saint' and 'hypocrite,' or 'saint' and 'not-saint'), they cannot in their nature be predicable in the same way of the same subject; and, therefore, in such a case 'either, or' means one or the other, but not both in the same relation.

Hence it seems necessary to admit that the conjunction 'either, or' may sometimes require one interpretation, sometimes the other; and the rule is that it implies the further possibility 'or both,' except when both alternatives have the same subject whilst the predicates are contrary or contradictory terms.
If, then, the disjunctive _A is either B or C_ (_B_ and _C_ being contraries) implies that both alternatives cannot be true, it can only be adequately rendered in hypotheticals by the two forms--( 1) _If A is B, it is not C_, and (2)_If A is not B, it is C_.