The principles which we have now stated are by no means alien to common apprehension: they are not absolutely hidden, perhaps, from any one, but are commonly seen through a mist. We might have presented the latter part of them in a phraseology in which they would have seemed the most familiar of truisms: we might have cautioned inquirers against too extensive generalization, and reminded them that there are exceptions to all rules. Such is the current language of those who distrust comprehensive thinking, without having any clear notion why or where it ought to be distrusted. We have avoided the use of these expressions purposely, because we deem them superficial and inaccurate. The error, when there is error, does not arise from generalizing too extensively; that is, from including too wide a range of particular cases in a single proposition. Doubtless, a man often asserts of an entire class what is only true of a part of it; but his error generally consists not in making too wide an assertion, but in making the wrong kind of assertion: he predicated an actual result, when he should only have predicated a tendency to that result—a power acting with a certain intensity in that direction. With regard to exceptions; in any tolerably ably advanced science there is properly no such thing as an exception. What is thought to be an exception to a principle is always some other and distinct principle cutting into the former: some other force which impinges against the first force, and deflects it from its direction. There are not a law and an exception to that law—the law acting in ninety-nine cases, and the exception in one. There are two laws, each possibly acting in the whole hundred cases, and bringing about a common effect by their conjunct operation. If the force which, being the less conspicuous of the two, is called the disturbing force, prevails sufficiently over the other force in some one case, to constitute that case what is commonly called an exception, the same disturbing force probably acts as a modifying cause in many other cases which no one will call exceptions.
Thus if it were stated to be a law of nature, that all heavy bodies fall to the ground, it would probably be said that the resistance of the atmosphere, which prevents a balloon from falling, constitutes the balloon an exception to that pretended law of nature. But the real law is, that all heavy bodies tend to fall; and to this there is no exception, not even the sun and moon; for even they, as every astronomer knows, tend towards the earth, with a force exactly equal to that with which the earth tends towards them. The resistance of the atmosphere might, in the particular case of the balloon, from a misapprehension of what the law of gravitation is, be said to prevail over the law; but its disturbing effect is quite as real in every other case, since though it does not prevent, it retards the fall of all bodies whatever. The rule, and the so-called exception, do not divide the cases between them; each of them is a comprehensive rule extending to all cases. To call one of these concurrent principles an exception to the other, is superficial, and contrary to the correct principles of nomenclature and arrangement. An effect of precisely the same kind, and arising from the same cause, ought not to be placed in two different categories, merely as there does or does not exist another cause preponderating over it.
It is only in art, as distinguished from science, that we can with propriety speak of exceptions. Art, the immediate end of which is practice, has nothing to do with causes, except as the means of bringing about effects. However heterogeneous the causes, it carries the effects of them all into one single reckoning, and according as the sum-total is plus or minus, according as it falls above or below a certain line, Art says, Do this, or Abstain from doing it. The exception does not run by insensible degrees into the rule, like what are called exceptions in science. In a question of practice it frequently happens that a certain thing is either fit to be done, or fit to be altogether abstained from, there being no medium. If, in the majority of cases, it is fit to be done, that is made the rule. When a case subsequently occurs in which the thing ought not to be done, an entirely new leaf is turned over; the rule is now done with, and dismissed: a new train of ideas is introduced, between which and those involved in the rule there is a broad line of demarcation; as broad and tranchant as the difference between Ay and No. Very possibly, between the last case which comes within the rule and the first of the exception, there is only the difference of a shade: but that shade probably makes the whole interval between acting in one way and in a totally different one. We may, therefore, in talking of art, unobjectionably speak of the rule and the exception; meaning by the rule, the cases in which there exists a preponderance, however slight, of inducements for acting in a particular way; and by the exception, the cases in which the preponderance is on the contrary side.
NOTES:
We say, the production and distribution, not, as is usual with writers on this science, the production, distribution, and consumption. For we contend that Political Economy, as conceived by those very writers, has nothing to do with the consumption of wealth, further than as the consideration of it is inseparable from that of production, or from that of distribution. We know not of any laws of the consumption of wealth as the subject of a distinct science: they can be no other than the laws of human enjoyment. Political economists have never treated of consumption on its own account, but always for the purpose of the inquiry in what manner different kinds of consumption affect the production and distribution of wealth. Under the head of Consumption, in professed treatises on the science, the following are the subjects treated of: 1st, The distinction between productive and unproductive consumption; 2nd, The inquiry whether it is possible for too much wealth to be produced, and for too great a portion of what has been produced to be applied to the purpose of further production; 3rd, The theory of taxation, that is to say, the following two questions—by whom each particular tax is paid (a question of distribution), and in what manner particular taxes affect production.
The physical laws of the production of useful objects are all equally presupposed by the science of Political Economy: most of them, however, it presupposes in the gross, seeming to say nothing about them. A few (such, for instance, as the decreasing ratio in which the produce of the soil is increased by an increased application of labour) it is obliged particularly to specify, and thus seems to borrow those truths from the physical sciences to which they properly belong, and include them among its own.