It has been proved at large, that the influence of belief is at once to inliven and infix any idea in the imagination, and prevent all kind of hesitation and uncertainty about it.  Both these circumstances are advantageous.  By the vivacity of the idea we interest the fancy, and produce, though in a lesser degree, the same pleasure, which arises from a moderate passion.  As the vivacity of the idea gives pleasure, so its certainty prevents uneasiness, by fixing one particular idea in the mind, and keeping it from wavering in the choice of its objects.  It is a quality of human nature, which is conspicuous on many occasions, and is common both to the mind and body, that too sudden and violent a change is unpleasant to us, and that however any objects may in themselves be indifferent, yet their alteration gives uneasiness.  As it is the nature of doubt to cause a variation in the thought, and transport us suddenly from one idea to another, it must of consequence be the occasion of pain.  This pain chiefly takes place, where interest, relation, or the greatness and novelty of any event interests us in it.  It is not every matter of fact, of which we have a curiosity to be informed; neither are they such only as we have an interest to know.  It is sufficient if the idea strikes on us with such force, and concerns us so nearly, as to give us an uneasiness in its instability and inconstancy.  A stranger, when he arrives first at any town, may be entirely indifferent about knowing the history and adventures of the inhabitants; but as he becomes farther acquainted with them, and has lived any considerable time among them, he acquires the same curiosity as the natives.  When we are reading the history of a nation, we may have an ardent desire of clearing up any doubt or difficulty, that occurs in it; but become careless in such researches, when the ideas of these events are, in a great measure, obliterated.

BOOK III OF MORALS

PART I OF VIRTUE AND VICE IN GENERAL

SECT.  I MORAL DISTINCTIONS NOT DERIVed FROM REASON

There is an inconvenience which attends all abstruse reasoning. that it may silence, without convincing an antagonist, and requires the same intense study to make us sensible of its force, that was at first requisite for its invention.  When we leave our closet, and engage in the common affairs of life, its conclusions seem to vanish, like the phantoms of the night on the appearance of the morning; and it is difficult for us to retain even that conviction, which we had attained with difficulty.  This is still more conspicuous in a long chain of reasoning, where we must preserve to the end the evidence of the first propositions, and where we often lose sight of ail the most received maxims, either of philosophy or common life.  I am not, however, without hopes, that the present system of philosophy will acquire