"we can know the true and unchanging meaning of dogmas"

". . . it must be stated that the dogmatic formulas of the Church's Magisterium were from the beginning suitable for communicating revealed truth, and that as they are they remain forever suitable for communicating this truth to those who interpret them correctly. It does not however follow that every one of these formulas has always been or will always be so to the same extent. . . .

"As for the meaning [(sensus)] of dogmatic formulas [(formularum)], this remains ever true and constant in the Church, even when it is expressed with greater clarity or more developed. The faithful therefore must shun the opinion, first, that dogmatic formulas (or some category of them) cannot signify truth in a determinate way, but can only offer changeable approximations to it, which to a certain extent distort or alter it; secondly, that these formulas signify the truth only in an indeterminate way, this truth being like a goal that is constantly being sought by means of such approximations. Those who hold such an opinion do not avoid dogmatic relativism and they corrupt the concept of the Church's infallibility relative to the truth to be taught or held in a determinate way.

". . . the meaning of dogmas which is declared by the Church is determinate and unalterable. . . .

". . . we can know the true and unchanging meaning of dogmas. What is new and what [John XXIII] recommends in view of the needs of the times pertains only to the modes of studying, expounding and presenting that doctrine while keeping its permanent meaning. . . ."

     Sacred Congregation for the Doctrine of the Faith, Mysterium ecclesiae, or Declaration in defense of the Catholic doctrine on the Church against certain errors of the present day 5, 24 June 1973.  Latin at AAS 65 (1973):  396-408, and here.

"Are we to continue in sin that grace may abound?"

"Sometimes it is necessary to drink a little more, play, jest, or even commit some sin in defiance and contempt of the devil [(atque adeo peccatum aliquod faciendum in odium et contemptum diaboli)] in order not to give him an opportunity to make us scrupulous about trifles [(ut conscientiam nobis faciat de rebus levissimis)].  We shall be overcome if we worry too much about falling into some sin.
     "Accordingly if the devil should say, 'Do not drink,' you should reply to him, 'On this very account, because you forbid it, I shall drink, and what is more, I shall drink a generous amount.'  Thus one must always do the opposite of what Satan prohibits.  What do you think is my reason for drinking wine undiluted, talking freely, and eating more often if it is not to torment and vex the devil who made up his mind to vex and torment me?  Would that I could [(Utinam possem)] commit some token sin simply for the sake of mocking the devil [(aliquid insigne peccati designare modo ad eludendem diabolum)], so that he might understand that I acknowledge no sin and am conscious of no sin.  When the Devil attacks and torments us, we must completely set aside the whole Decalogue [(Omnino totus decalogus amovendus est nobis ex oculis et animo)].  When the devil throws our sins up to us and declares that we deserve death and hell, we ought to speak thus:  'I admit that I deserve death and hell.  What of it?  Does this mean that I shall be sentenced to eternal damnation?  By no means.  For I know One who suffered and made satisfaction in my behalf.  His name is Jesus Christ, the Son of God.  Where he is, there I shall be also.'"

     Martin Luther, letter no. 1670 to Jerome Weller, July 1530, as trans. Theodore G. Tappert on p. 86-87 (84-87) of Luther:  letters of spiritual counsel, LCC 18 (Philadelphia:  The Westminster Press, 1955), underscoring mine.  Latin from WA Br 5, 518-520.  Would that I could.  some token of sin.  Still, . . .
     I get the point of the hyperbole.  And yet Luther seems downright irresponsible here.  In order to do always "the opposite of what Satan prohibits" should we do also what God does (i.e. probibits) explicitly?  Probably Luther has in mind really only diabolic interpretations of the Decalogue.  But this language is too reckless for me.