The Christian concept of internal sin is the idea that
sin (a crime of religion) may be committed not only by outward deeds but also by the inner activity of the mind, quite apart from any external manifestation.
Thought crimes were as old as
heresy, but the
Reformation's alarms received new emphasis at the
Council of Trent (Session XIV, chapter. v). The session, while reiterating that all
mortal sins must be confessed, singled out the unspoken ones that "sometimes more grievously wound the soul and are more dangerous than sins which are openly committed".
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