Jonathan Edwards writes:
We see the world of mankind to be exceedingly busy and active; and the affections of men are the springs of the motion: take away all love and hatred, all hope and fear, all anger, zeal and affectionate desire, and the world would be, in a great measure, motionless and dead; there would be no such thing as activity amongst mankind, or any earnest pursuit whatsoever. ‘Tis affection that engages the covetous man, and him that is greedy of worldly profits, in his pursuits; and it is by the affections, that the [sinfully] ambitious man is put forward in his pursuit of worldly glory; and ’tis the affections also that actuate the voluptuous man, in his pursuit of pleasure and sensual delights: the world continues, from age to age, in a continual commotion and agitation, in a pursuit of these things; but take away all affection, and the spring of all this motion would be gone, and the motion itself would cease. And as in worldly things, worldly affections are very much the spring of men’s motion and action; so in religious matters, the spring of their actions are very much religious affections: he that has doctrinal knowledge and speculation only, without affection, never is engaged in the business of religion.
-Jonathan Edwards, Religious Affections (Yale) 2:110.
(HT: Tony Reinke)