All resembling impressions are connected together, and no sooner one arises than the rest immediately follow.
Grief and disappointment give rise to anger, anger to envy, envy to malice, and malice to grief again, till the whole circle be compleated.
In like manner our temper, when elevated with joy, naturally throws itself into love, generosity, pity, courage, pride, and the other resembling affections.

It is difficult for the mind, when actuated by any passion, to confine itself to that passion alone, without any change or variation.

Human nature is too inconstant to admit of any such regularity.

Changeableness is essential to it.

And to what can it so naturally change as to affections or emotions, which are suitable to the temper, and agree with that set of passions, which then prevail?
It is evident, then, there is an attraction or association among impressions, as well as among ideas; though with this remarkable difference, that ideas are associated by resemblance, contiguity, and causation; and impressions only by resemblance.
In the THIRD place, it is observable of these two kinds of association, that they very much assist and forward each other, and that the transition is more easily made where they both concur in the same object.