Mean while to give a solution of the preceding objection upon the supposition, that historical evidence amounts at first to an entire proof; let us consider, that though the links are innumerable, that connect any original fact with the present impression, which is the foundation of belief; yet they are all of the same kind, and depend on the fidelity of Printers and Copyists. One edition passes into another, and that into a third, and so on, till we come to that volume we peruse at present. There is no variation in the steps. After we know one we know all of them; and after we have made one, we can have no scruple as to the rest. This circumstance alone preserves the evidence of history, and will perpetuate the memory of the present age to the latest posterity.

If all the long chain of causes and effects, which connect any past event with any volume of history, were composed of parts different from each other, and which it were necessary for the mind distinctly to conceive, it is impossible we should preserve to the end any belief or evidence. But as most of these proofs are perfectly resembling, the mind runs easily along them, jumps from one part to another with facility, and forms but a confused and general notion of each link. By this means a long chain of argument, has as little effect in diminishing the original vivacity, as a much shorter would have, if composed of parts, which were different from each other, and of which each required a distinct consideration.

A fourth unphilosophical species of probability is that derived from general rules, which we rashly form to ourselves, and which are the source of what we properly call PREJUDICE. An IRISHMAN cannot have wit, and a Frenchman cannot have solidity; for which reason, though the conversation of the former in any instance be visibly very agreeable, and of the latter very judicious, we have entertained such a prejudice against them, that they must be dunces or fops in spite of sense and reason. Human nature is very subject to errors of this kind; and perhaps this nation as much as any other.

Should it be demanded why men form general rules, and allow them to influence their judgment, even contrary to present observation and experience, I should reply, that in my opinion it proceeds from those very principles, on which all judgments concerning causes and effects depend. Our judgments concerning cause and effect are derived from habit and experience; and when we have been accustomed to see one object united to another, our imagination passes from the first to the second, by a natural transition, which precedes reflection, and which cannot be prevented by it. Now it is the nature of custom not only to operate with its full force, when objects are presented, that are exactly the same with those to which we have been accustomed; but also to operate in an inferior degree, when we discover such as are similar; and though the habit loses somewhat of its force by every difference, yet it is seldom entirely destroyed, where any considerable circumstances remain the same. A man, who has contracted a custom of eating fruit by the use of pears or peaches, will satisfy himself with melons, where he cannot find his favourite fruit; as one, who has become a drunkard by the use of red wines, will be carried almost with the same violence to white, if presented to him. From this principle I have accounted for that species of probability, derived from analogy, where we transfer our experience in past instances to objects which are resembling, but are not exactly the same with those concerning which we have had experience.

In proportion as the resemblance decays, the probability diminishes; but still has some force as long as there remain any traces of the resemblance.

This observation we may carry farther; and may remark, that though custom be the foundation of all our judgments, yet sometimes it has an effect on the imagination in opposition to the judgment, and produces a contrariety in our sentiments concerning the same object. I explain myself. In almost all kinds of causes there is a complication of circumstances, of which some are essential, and others superfluous; some are absolutely requisite to the production of the effect, and others are only conjoined by accident. Now we may observe, that when these superfluous circumstances are numerous, and remarkable, and frequently conjoined with the essential, they have such an influence on the imagination, that even in the absence of the latter they carry us on to the conception of the usual effect, and give to that conception a force and vivacity, which make it superior to the mere fictions of the fancy. We may correct this propensity by a reflection on the nature of those circumstances: but it is still certain, that custom takes the start, and gives a biass to the imagination.

To illustrate this by a familiar instance, let us consider the case of a man, who, being hung out from a high tower in a cage of iron cannot forbear trembling, when he surveys the precipice below him, though he knows himself to be perfectly secure from falling, by his experience of the solidity of the iron, which supports him; and though the ideas of fall and descent, and harm and death, be derived solely from custom and experience. The same custom goes beyond the instances, from which it is derived, and to which it perfectly corresponds; and influences his ideas of such objects as are in some respect resembling, but fall not precisely under the same rule. The circumstances of depth and descent strike so strongly upon him, that their influence can-not be destroyed by the contrary circumstances of support and solidity, which ought to give him a perfect security. His imagination runs away with its object, and excites a passion proportioned to it. That passion returns back upon the imagination and inlivens the idea; which lively idea has a new influence on the passion, and in its turn augments its force and violence; and both his fancy and affections, thus mutually supporting each other, cause the whole to have a very great influence upon him.

But why need we seek for other instances, while the present subject of philosophical probabilities offers us so obvious an one, in the opposition betwixt the judgment and imagination arising from these effects of custom? According to my system, all reasonings are nothing but the effects of custom; and custom has no influence, but by inlivening the imagination, and giving us a strong conception of any object. It may, therefore, be concluded, that our judgment and imagination can never be contrary, and that custom cannot operate on the latter faculty after such a manner, as to render it opposite to the former. This difficulty we can remove after no other manner, than by supposing the influence of general rules. We shall afterwards take[10] notice of some general rules, by which we ought to regulate our judgment concerning causes and effects; and these rules are formed on the nature of our understanding, and on our experience of its operations in the judgments we form concerning objects.

By them we learn to distinguish the accidental circumstances from the efficacious causes; and when we find that an effect can be produced without the concurrence of any particular circumstance, we conclude that that circumstance makes not a part of the efficacious cause, however frequently conjoined with it. But as this frequent conjunction necessity makes it have some effect on the imagination, in spite of the opposite conclusion from general rules, the opposition of these two principles produces a contrariety in our thoughts, and causes us to ascribe the one inference to our judgment, and the other to our imagination. The general rule is attributed to our judgment; as being more extensive and constant. The exception to the imagination, as being more capricious and uncertain.

[10] Sect. 15.

Thus our general rules are in a manner set in opposition to each other. When an object appears, that resembles any cause in very considerable circumstances, the imagination naturally carries us to a lively conception of the usual effect, Though the object be different in the most material and most efficacious circumstances from that cause. Here is the first influence of general rules. But when we take a review of this act of the mind, and compare it with the more general and authentic operations of the understanding, we find it to be of an irregular nature, and destructive of all the most established principles of reasonings; which is the cause of our rejecting it. This is a second influence of general rules, and implies the condemnation of the former.

Sometimes the one, sometimes the other prevails, according to the disposition and character of the person. The vulgar are commonly guided by the first, and wise men by the second. Mean while the sceptics may here have the pleasure of observing a new and signal contradiction in our reason, and of seeing all philosophy ready to be subverted by a principle of human nature, and again saved by a new direction of the very same principle. The following of general rules is a very unphilosophical species of probability; and yet it is only by following them that we can correct this, and all other unphilosophical probabilities.

Since we have instances, where general rules operate on the imagination even contrary to the judgment, we need not be surprized to see their effects encrease, when conjoined with that latter faculty, and to observe that they bestow on the ideas they present to us a force superior to what attends any other. Every one knows, there is an indirect manner of insinuating praise or blame, which is much less shocking than the open flattery or censure of any person. However he may communicate his sentiments by such secret insinuations, and make them known with equal certainty as by the open discovery of them, it is certain that their influence is not equally strong and powerful. One who lashes me with concealed strokes of satire, moves not my indignation to such a degree, as if he flatly told me I was a fool and coxcomb; though I equally understand his meaning, as if he did. This difference is to be attributed to the influence of general rules.

Whether a person openly, abuses me, or slyly intimates his contempt, in neither case do I immediately perceive his sentiment or opinion; and it is only by signs, that is, by its effects, I become sensible of it. The only difference, then, betwixt these two cases consists in this, that in the open discovery of his sentiments he makes use of signs, which are general and universal; and in the secret intimation employs such as are more singular and uncommon. The effect of this circumstance is, that the imagination, in running from the present impression to the absent idea, makes the transition with greater facility, and consequently conceives the object with greater force, where the connexion is common and universal, than where it is more rare and particular. Accordingly we may observe, that the open declaration of our sentiments is called the taking off the mask, as the secret intimation of our opinions is said to be the veiling of them. The difference betwixt an idea produced by a general connexion, and that arising from a particular one is here compared to the difference betwixt an impression and an idea.