Repeated vice hardens a person until virtue becomes impossible.

Evidence

On the other hand, the more one gives in to vice, the harder it is to act virtuously. This is precisely how many Muslims interpret the repeated Qur’anic declaration to the effect that God seals the hearts of stubborn sinners. The punishment for repeated wickedness is to become the sort of person one is: unable to distinguish true speech from false, and divine speech from human speech—a person who cannot live the virtuous life that God requires of her or him. Time is not reversible. — Talal Asad, Formations of the Secular, 438

Categorization

• DEFINE: Clarifies the Qur’anic ‘sealing of hearts’ as a natural consequence of repeated sin rather than arbitrary divine decree.
• XREF: Dovetails with Aristotle’s habituation ethics (‘we become what we repeatedly do’) and with Butler’s Parable of the Sower on how character crystallizes under repeated practice.
• SHARE: Worth sending to anyone who argues free will means we can always change—this is a tradition that takes the irreversible hardening of character seriously.