Roscoe have you actually studied any Catholic Moral Theology or are you self-taught?
The CCC is a summary not a course in moral theology and it cannot be expected to articulate the very tight Thomist philosophical underpinnings of its statements.
Your above statement suggests you do not really understand what a moral human act is in Moral Theology.
An objedctive physical action (eg amputation) is not yet a human act and therefore cannot be called good, bad sad or mad. Therefore it is not yet in the category “moral” (moral means an act involving known human choice, intention and purpose.)
This is a Moral Theology forum. If you don’t possess the basic cooking skills I suggest you stay out of the kitchen or assume a more open stance so those who actually are trained chefs may be able to dialogue rationally with you

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I repeat, we need to know why the “amputee” wanted his arm amputated before we can judge the moral nature of that human act. If his purpose was to live then this amputation is good. If it was because he lost a bet (“I’ll bet my right arm…”) then it is evil. Evil acts of amputation are called mutilations. “Mutilation” describes a complete human act which involves disordered purpose.
That is why “mutilation” is a always an intrinsically evil act so far as Moral Theology is concerned.
“Multilation”, in medical terms, is not the same. Doctors commonly mean just the “object” or external “procedure” of the moral act which is always neutral if intention/purpose is unknown.
This is where you are going wrong and why you misundertand the CCC.
You think theologians and doctors use these words in the same way. They don’t.
I accept that the CCC (in English as translated by the USBishops Conference) is translated poorly re the word “mutilation” - but then the CCC is not meant for moral theology students but for ordinary lay people. Clearly the word “mutilation” is used in its normal english lay sense (simply describing a non-moral external medical procedure).
If you check the Latin CCC (ie the actual CCC) I believe you will find the word translated to “mutilation” prob has no pejorative overtones at all.