A man, brought to the brink of a precipice, cannot look down
without trembling; and the sentiment of IMAGINARY danger actuates
him, in opposition to the opinion and belief of REAL safety. But
the imagination is here assisted by the presence of a striking
object; and yet prevails not, except it be also aided by novelty,
and the unusual appearance of the object. Custom soon reconciles
us to heights and precipices, and wears off these false and
delusive terrors. The reverse is observable in the estimates
which we form of characters and manners; and the more we
habituate ourselves to an accurate scrutiny of morals, the more
delicate feeling do we acquire of the most minute distinctions
between vice and virtue. Such frequent occasion, indeed, have we,
in common life, to pronounce all kinds of moral determinations,
that no object of this kind can be new or unusual to us; nor
could any FALSE views or prepossessions maintain their ground
against an experience, so common and familiar. Experience being
chiefly what forms the associations of ideas, it is impossible
that any association could establish and support itself, in
direct opposition to that principle.

Usefulness is agreeable, and engages our approbation. This is a
matter of fact, confirmed by daily observation. But, USEFUL? For
what? For somebody's interest, surely. Whose interest then? Not
our own only: For our approbation frequently extends farther. It
must, therefore, be the interest of those, who are served by the
character or action approved of; and these we may conclude,
however remote, are not totally indifferent to us. By opening up
this principle, we shall discover one great source of moral
distinctions.