What Is The Difference Between "illicit" And "invalid"

[Gabriela]

With regards to the consecration, what is the difference between (il)licit and (in)valid?

[cappie]

Illicit means not legal. Invalid means not effective. Lets say for example that a priest changes the words of the Credo or Creed in the Mass or the priest used bread that according to the Roman Rite is not leavened . That would be illicit, but it would still be a valid Mass and the bread and wine would be changed into the body, blood, soul, and divinity of Jesus. If that same priest decided to not use the words of consecration,  This is my body...., This is my blood...., or use matter other than bread and wine then the Mass would be invalid and not truly a Mass.

 

Another example from another sacrament  might be a lay person who decides in a non-emergency to baptize a baby using the proper words and actions, that would be illicit, but the baptism would be valid. Same person attempts to baptize that baby, uses water, but does not use the proper formula of words. The baptism would be invalid, i.e. not effective.