  One possibility is that logicians previous to the 20th century must have thought that no terms are empty. You see this view referred to frequently as one that others  held.[3]  But with a few very special exceptions (discussed below) I have been unable to find anyone who held such a view before the nineteenth century. Many authors do not discuss empty terms, but those who do typically take their presence for granted. Explicitly rejecting empty terms was never a mainstream option, even in the nineteenth century.