Christopher Hitchen's quoting F.M. Cornford's "Microcosmographia Academica" in his "Letters to a Young Contrarian"

There is only one argument for doing something; the rest are arguments for doing nothing.

Since the stone axe fell into disuse at the close of the Neolithic Age, two other arguments of universal application have been added to the rhetorical armoury by the ingenuity of mankind. They are closely akin; and, like the stone axe, they are addressed to the Political Motive. They are called the Wedge and the Dangerous Precedent. Though they are very familiar, the principles, or rules of inaction, involved in them are seldom stated in full. They are as follows:

The Principle of the Wedge is that you should not act justly now for fear of raising expectations that you may act still more justly in the future--expectations that you are afraid you will not have the courage to satisfy. A little reflection will make it evident that the Wedge argument implies the admission that the persons who use it cannot prove that the action is not just. If they could, that would be the sole and sufficient reason for not doing it, and this argument would be superfluous.

The Principle of the Dangerous Precedent is that you should not now do any admittedly right action for fear, or your equally timid successors, should not have the courage to do right in some future case, which, ex hypothesi, is essentially different, but superficially resembles the present one. Every public action that is not customary, either is wrong, or, if it is right, is a dangerous precedent. It follows that nothing should ever be done for the first time.

Another argument is that "the Time is not Ripe." The Principle of Unripe Time is that people should not do at the present moment what they think right at that moment, because the moment at which they think it right has not yet arrived. 

You may, and I assure you of this, be certain that you will meet some combination of these arguments and evasions as you go through life. you may not always have the energy to combat each of them every time; you may find that you want to husband and conserve your resources for a better cause or a more propitious day. Beware of this tendency in yourself. Be alert, especially, for that awful day when--without even having meant to do so--you find that you have uttered one of these consoling and corrupting formulations yourself.