The Commens Dictionary
Quote from ‘Lowell Lectures. 1903. Lecture 3’
A Collection is anything whose being consists in the existence of whatever there may exist that has any one quality; and if such thing or things exist, the collection is a single thing whose existence consists in the existence of all those very things.
According to this definition, a collection is an ens rationis. [—] A collection has essence and may have existence.