Are brief blasphemous deliberate thoughts a mortal sin according to Catholicism?

1 Answer 1


Mortal sin (from mors = death) forfeits sanctifying grace and is the supernatural death of the soul. St. Augustine defines it as "something said, done or desired contrary to the eternal law."

To be a mortal sin, these conditions must be satisfied:

  1. Knowledge (either natural or supernatural) of the act's sinfulness (offense to God).

  2. Freely performing the sin.

  3. Grave matter

In your scenario, #2 is satisfied because you say "deliberate". #3 is satisfied because blasphemy is a grave offense against God.

It's unclear if #1 is satisfied, you should confess it to a priest, who can help judge if such a sin is mortal.

  • The fact that the question was asked here suggests that condition #1 was not satisfied yesterday (but maybe it is satisfied now). Commented Nov 17, 2018 at 16:21

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