In other words, though the word “insurrection” seems to be plain in meaning, yet when we make it one term of a judgment of which the other term is “justifiable,” we find that we do not know whether we agree or not.  The terms of the proposition are so vague that there can be no meeting of minds.  If we limit the subject to a specific case, insurrection in Venezuela, or insurrection in Cuba, then we have made a beginning toward making the proposition arguable.  In these particular cases, however, it would probably be necessary to go further, and specify which insurrection in Venezuela or in Cuba was intended, before the average American would be prepared either to affirm or to deny.  Wherever the terms of a proposition are too vague to provoke profitable discussion they must be narrowed down to a specific case which will draw forth affirmation and denial.

A common case where the vagueness of the proposition leads to difficulties in the argument is described in the following passage: 

* * * * *

An equally common form of argument, closely allied to the argument by analogy, and equally vague, is that which is popularly known as the objection to a thin end of a wedge.  We must not do this or that, it is often said, because if we did we should be logically bound to do something else which is plainly absurd or wrong.  If we once begin to take a certain course there is no knowing where we shall be able to stop with any show of consistency; there would be no reason for stopping anywhere in particular, and we should be led on, step by step, into action or opinions that we all agree to call undesirable or untrue....

For it must not be forgotten that in all disputes of this kind there are two parties opposed to each other, and that what divides them is precisely their lack of agreement on the question what principle is really involved.  Those who see a proposal as a thin end of a wedge always see the principle as a wider, more inclusive one, than those who make the proposal; and what gives them freedom so to see it is merely the fact that it remains indefinite.[5]

As a practical example of this confusion, consider the following extract from a speech in the United States Senate opposing the popular election of senators: 

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Every intelligent student of the present rapid trend toward popular government must see what would happen when this sentimental bar of the States being represented by two Senators instead of by the people in the United States Senate is thrown down.  The initiative, the referendum, and the recall are but symptoms of the times.  That the people will have their way, because they, and they alone, are the government, is the underlying spirit of our institutions, of our newest State Constitutions, and of our progressive laws.  Skillful agitation seizes upon every pretext and eagerly grasps and enlarges every opportunity for appeal to the passions in an advancement of its purposes.  The next cry will necessarily be, “Why not elect the Supreme Court of the United States by popular vote?  Why not elect the Federal Judiciary everywhere by popular vote?"[6]