I understand that Jesus fulfils the OT ritual laws and one's country's laws replaces the OT civil laws, leaving Catholics with only the OT moral laws plus the 10 commandments.

How do Catholics determine whether a commandment is a moral law and binding?

For example, ploughing with an ox and an ass in the same yoke (Deut 22:10). Is this some spiritual purity law or is this about compassion to the animals (for the ox will push harder than the ass and drag it along)?

What of laws with both ritual and moral components, such as the Sabbatical year which frees slaves and annuls debts as well as forbids planting?

Is there a rule or did they just discuss it in a synod?

  • One obvious rule for universal laws would be when God calls something "an abomination" or refers to something as "my" or "of the Lord", then that attribute must be intrinsic to the thing itself, not a result of civil or levitical laws. The Catholic Church clearly doesn't follow this rule though. Commented Sep 9, 2022 at 23:25
  • Certain insects are described as abominations with regard to eating them but I've never heard of a Christian being restricted from any kind of food (except meat in Fridays!) Commented Sep 11, 2022 at 2:07
  • Eating pork and shellfish are also called abominations, but as I said, the Catholic Church clearly doesn't follow this rule. ¶ (Some Christian denominations do follow God's teaching literally though. E.g. 7th Day Adventists and various Church of God organizations (What Does the Bible Teach About Clean and Unclean Meats?).) Commented Sep 11, 2022 at 2:28

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The NT introduces a new dimension to many of the laws " Although Aquinas believed the specifics of the Old Testament judicial laws were no longer binding, he taught that the judicial precepts contained universal principles of justice that reflected natural law."

Just as the Commandment against murder only added a divine sanction against something everybody already known from reason as wrong. So now God was saying "murder is wrong as you know but it is also killing one of my children so you have committed a divine offense in doing this"

The mixing of fabrics and beasts was a physical exemplification of the spiritual truth about 1) doing the right thing even if you don't grasp why and 2) that there are natures to things and they should be respected.

Hence this has 2 levels of meaning: “You shall not lie with a male as with a woman; it is an abomination.”

  • So only commandments derivable from reason remain binding. What are the first principles to begin this derivation? Commented Oct 3, 2022 at 19:26

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