So that when I speak of cause, and efficient cause, I only mean certain affections of the mind, that cause certain changes in the body; or certain powers and properties in bodies, that work a change in the mind.

As, if I were to explain the motion of a body falling to the ground, I would say it was caused by gravity; and I would endeavor to show after what manner this power operated, without attempting to show why it operated in this manner: or, if I were to explain the effects of bodies striking one another by the common laws of percussion, I should not endeavor to explain how motion itself is communicated.
SECTION II.
ASSOCIATION.
It is no small bar in the way of our inquiry into the cause of our passions, that the occasions of many of them are given, and that their governing motions are communicated at a time when we have not capacity to reflect on them; at a time of which all sort of memory is worn out of our minds.

For besides such things as affect us in various manners, according to their natural powers, there are associations made at that early season, which we find it very hard afterwards to distinguish from natural effects.

Not to mention the unaccountable antipathies which we find in many persons, we all find it impossible to remember when a steep became more terrible than a plain; or fire or water more terrible than a clod of earth; though all these are very probably either conclusions from experience, or arising from the premonitions of others; and some of them impressed, in all likelihood, pretty late.

But as it must be allowed that many things affect us after a certain manner, not by any natural powers they have for that purpose, but by association; so it would be absurd, on the other hand, to say that all things affect us by association only; since some things must have been originally and naturally agreeable or disagreeable, from which the others derive their associated powers; and it would be, I fancy, to little purpose to look for the cause of our passions in association, until we fail of it in the natural properties of things.
SECTION III.
CAUSE OF PAIN AND FEAR.
I have before observed,[29] that whatever is qualified to cause terror is a foundation capable of the sublime; to which I add, that not only these, but many things from which we cannot probably apprehend any danger, have a similar effect, because they operate in a similar manner.
I observed, too,[30] that whatever produces pleasure, positive and original pleasure, is fit to have beauty engrafted on it.