More than other sins, the definition of sloth has changed
considerably since its original inclusion among the seven deadly sins.
In fact it was first called the sin of sadness or despair. It had been
in the early years of Christianity characterized by what modern
writers would now describe as melancholy: apathy, depression, and
joylessness — the last being viewed as being a refusal to enjoy the
goodness of God and the world God created. Originally, its place was
fulfilled by two other aspects, acedia and sadness. The former
described a spiritual apathy that affected the faithful by
discouraging them from their religious work. Sadness (tristitia in
Latin) described a feeling of dissatisfaction or discontent, which
caused unhappiness with one's current situation. When Thomas Aquinas
selected acedia for his list, he described it as an "uneasiness of the
mind", being a progenitor for lesser sins such as restlessness and
instability. Dante refined this definition further, describing sloth
as being the "failure to love God with all one's heart, all one's mind
and all one's soul." He also described it as the middle sin, and as
such was the only sin characterised by an absence or insufficiency of
love. In his "Purgatorio", the slothful penitents were made to run
continuously at top speed.
The modern view of the vice, as highlighted by its contrary virtue of
zeal or diligence, is that it represents the failure to utilize one's
talents and gifts. For example, a student who does not work beyond
what is required (and thus fails to achieve his or her full potential)
could be labeled slothful.
Current interpretations are therefore much less stringent and
comprehensive than they were in medieval times, and portray sloth as
being more simply a sin of laziness or indifference, of an
unwillingness to act, an unwillingness to care (rather than a failure
to love God and his works). For this reason sloth is now often seen as
being considerably less serious than the other sins, more a sin of
omission than of commission.