Now if we compare these two cases, of the open and concealed violations of the laws of honour, we shall find, that the difference betwixt them consists in this, that in the first ease the sign, from which we infer the blameable action, is single, and suffices alone to be the foundation of our reasoning and judgment; whereas in the latter the signs are numerous, and decide little or nothing when alone and unaccompanyed with many minute circumstances, which are almost imperceptible.  But it is certainly true, that any reasoning is always the more convincing, the more single and united it is to the eye, and the less exercise it gives to the imagination to collect all its parts, and run from them to the correlative idea, which forms the conclusion.  The labour of the thought disturbs the regular progress of the sentiments, as we shall observe presently.[Part IV.  Sect. 1.] The idea strikes not on us with ouch vivacity; and consequently has no such influence on the passion and imagination.

From the same principles we may account for those observations of the cardinal de Retz, that there are many things, in which the world wishes to be deceived; and that it more easily excuses a person in acting than in talking contrary to the decorum of his profession and character.  A fault in words is commonly more open and distinct than one in actions, which admit of many palliating excuses, and decide not so clearly concerning the intention and views of the actor.

Thus it appears upon the whole, that every kind of opinion or judgment, which amounts not to knowledge, is derived entirely from the force and vivacity of the perception, and that these qualities constitute in the mind, what we call the belief Of the existence of any object.  This force and this vivacity are most conspicuous in the memory; and therefore our confidence in the veracity of that faculty is the greatest imaginable, and equals in many respects the assurance of a demonstration.  The next degree of these qualities is that derived from the relation of cause and effect; and this too is very great, especially when the conjunction is found by experience to be perfectly constant, and when the object, which is present to us, exactly resembles those, of which we have had experience.  But below this degree of evidence there are many others, which have an influence on the passions and imagination, proportioned to that degree of force and vivacity, which they communicate to the ideas.  It is by habit we make the transition from cause to effect; and it is from some present impression we borrow that vivacity, which we diffuse over the correlative idea.  But when we have not observed a sufficient number of instances, to produce a strong habit; or when these instances are contrary to each other; or when the resemblance is not exact; or the present impression is faint and obscure; or the experience in some measure obliterated from the memory; or the connexion dependent on a long chain of objects; or the inference derived from general rules, and yet not conformable to them:  In all these cases the evidence diminishes by the diminution of the force and intenseness of the idea.  This therefore is the nature of the judgment and probability.