A mountain neither magnifies nor diminishes a horse in our eyes; but when a Flemish and a Welsh horse are seen together, the one appears greater and the other less, than when viewed apart.
From the same principle we may account for that remark of historians, that any party in a civil war always choose to call in a foreign enemy at any hazard rather than submit to their fellow-citizens.

Guicciardin applies this remark to the wars in Italy, where the relations betwixt the different states are, properly speaking, nothing but of name, language, and contiguity.

Yet even these relations, when joined with superiority, by making the comparison more natural, make it likewise more grievous, and cause men to search for some other superiority, which may be attended with no relation, and by that means may have a less sensible influence on the imagination.

The mind quickly perceives its several advantages and disadvantages; and finding its situation to be most uneasy, where superiority is conjoined with other relations, seeks its repose as much as possible, by their separation, and by breaking that association of ideas, which renders the comparison so much more natural and efficacious.

When it cannot break the association, it feels a stronger desire to remove the superiority; and this is the reason why travellers are commonly so lavish of their praises to the Chinese and Persians, at the same time, that they depreciate those neighbouring nations, which may stand upon a foot of rivalship with their native country.
These examples from history and common experience are rich and curious; but we may find parallel ones in the arts, which are no less remarkable.
should an author compose a treatise, of which one part was serious and profound, another light and humorous, every one would condemn so strange a mixture, and would accuse him of the neglect of all rules of art and criticism.