Middle English slouthe, from slow. Webster 1828: "disinclination to action or labor; sluggishness; laziness; idleness." In classical Christian moral theology, one of the seven deadly sins (Latin acedia, Greek akēdia — "not caring, listlessness, spiritual torpor"). Sloth is more than mere laziness; it is refusal of the spiritual good one knows, the dispirited avoidance of the effort holiness requires. Aquinas defined it as "sorrow about spiritual good" — a reluctance to pursue God even when the beauty of God is clearly seen.
Sloth is the subtlest of the deadly sins and perhaps the most common in comfortable cultures. Three observations. (1) Spiritual, not merely physical. A workaholic executive can be slothful while exhausted in career; a diligent student can be slothful in prayer. Sloth is not a failure to do something; it is a failure to love the right things enough to do them. The slothful Christian may attend every meeting at church and still be slothful toward God in his heart. (2) Produces "the noonday devil". The desert fathers called sloth the noonday devil — the midday moment in the monastic cell when boredom and dispiritedness hit hardest. The cure, the fathers said, is stability — stay in the cell, stay at the task, stay in the vocation God assigned. Fleeing to novelty only trains the soul to flee. (3) Opposed by zeal. "Never be lazy [oknēros] in zeal, be fervent in spirit, serve the Lord" (Romans 12:11). Zeal (zelos) is the opposite of sloth — a burning commitment to God's glory that labors, endures, and rejoices in the pursuit of what matters. The sloth-tempted Christian needs to rekindle the love that makes obedience feel like feasting rather than chore. Dante in the Purgatorio pictures the slothful running endlessly to purge their past refusal to run. Pray against sloth daily — ask God for warmed affections and renewed zeal.