The earth hath bubbles as the water hath,
And these are of them.
A development is such an ambiguous expression (for it may be either good, bad or indifferent) that, on that understanding, we may freely admit its existence; but an extension of principle has several varieties, is as slippery as an eel, and both the extension and the principle must be regarded with a wary eye.
The principle that is extended by substituting ‘always’ for ‘generally’ and then appealing boldly to history to sanction the alteration is one form. Another form is to invent both the principle and the extension when the occasion arises, as in the principle of leading the bottom of an intermediate sequence, and its extension to penultimates, antepenultimates, and so forth. Logicians term this petitio, not extensio principii.
Even when you have got firm hold of a good principle, or a good india-rubber ring, you will get into trouble if you stretch it indefinitely.
There is no sounder principle going than that it is generally desirable to acquaint your partner with the state of your hand, but it neither follows that you should place it face upwards on the table, nor avail yourself of those extensions known to Hoyle as “piping at whisk,” though the first is undoubtedly legitimate, and the second, if it were only first duly exploited by some faddist in The Field, would be quite as legitimate as any extension that has appeared there in our time.
While these extensions of principle are in the air, some regard should be paid to the interests of that numerous class whose information is entirely derived from inspection of the last trick. Already they had to find out in that obscure medium what suit was led, who led it, and how each card fell. Now, they have in addition, to track to their lair several missing minor cards, and when they have succeeded in doing so, to decide whether they indicate a signal, a nine suit, the lowest of a long head sequence, or the lunacy of the leader. If their happiness is to be taken into consideration one important extension of principle must be added to the list.
It is a principle—vide law 91—that we may all see the penultimate trick, and the extension that we may all see the antepenultimate and so on up to thirteen, proceeds pari passu with the other famous demonstration; it also conveys the same kind of information, in exactly the same way, for it shows those who have eyes in their heads that which they already knew, and reduces to a more hopeless state of imbecility those dependent on its aid.
I do not advocate it for two reasons; in the first place, because I abjure and detest the principle itself; secondly, because the only time I ever attempted to extend a principle, I was accused of sorites, which sounds like some unpleasant form of skin disease, and such insinuations, though untrue, are disagreeable. As I do not wish to expose myself to them, I make a present of the idea to any pupil of the new academy who may be intent on further spoiling the game.