A Legitimate Answer
To a typically condescending question
If you’re like me, you’ve likely encountered someone asking you, a Christian, the pointed question that goes something like this: "You know… if you don’t think eating shellfish is a sin, then why do you say X is, since they’re both from the Old Testament?”
This, of course, takes many more forms than just this. One interlocutor may produce shellfish as their example, while others will bring up sowing multiple seeds in a field, wearing mixed fibers, or animal sacrifice.
This question is generally meant as a dismissal, not an inquiry, but nonetheless it’s important to have an answer. I suspect the reasons these laws get brought up over and over is two-fold. First, their proximity to the Holiness Code implies that they are of equal weight as the sexual prohibitions found therein. Secondly, I suspect these objections are raised repeatedly because there’s a distinct lack of a satisfying answer that comes from the most visible apologists.
The answer one will typically hear from street preachers or professional apologists is something akin to “that’s a different type of law”. While the tripartite distinction of the law can be an interesting theological discussion, it’s both underwhelming for a non-believer, and legitimately comes across as a dodge. To be clear, I think that we can explain why these laws don’t apply through a tripartite distinction, but I don’t think it’s necessary. In fact, I think there’s a much better way, and it’s found in the New Testament.
We as followers of Christ also are followers of His Apostles. The conciliar nature of the Church is such that if a disagreement arises, Church authorities gather in a council to address concerns. This is how the Church came to condemn Arianism and Nestorianism, for instance. However, even before the Christian faith was legalized in the Roman Empire, allowing for councils to take place publicly, there was a council recorded in Scripture. The Apostles gathered together to settle the dispute over the extent to which the Gentile converts were required to follow the Torah, as was the custom of the ancient (Jewish) converts. A full reading of Acts 15 gives the best picture, but ultimately St. James, and the subsequent encyclical that was distributed to the Churches, proclaims that we should only burden Gentile converts with the following:
The apostles, the elders, and the brethren,
To the brethren who are of the Gentiles in Antioch, Syria, and Cilicia:
Greetings.
Since we have heard that some who went out from us have troubled you with words, unsettling your souls, saying, “You must be circumcised and keep the law”—to whom we gave no such commandment— it seemed good to us, being assembled with one accord, to send chosen men to you with our beloved Barnabas and Paul, men who have risked their lives for the name of our Lord Jesus Christ. We have therefore sent Judas and Silas, who will also report the same things by word of mouth. For it seemed good to the Holy Spirit, and to us, to lay upon you no greater burden than these necessary things: that you abstain from things offered to idols, from blood, from things strangled, and from sexual immorality. If you keep yourselves from these, you will do well.
Farewell.
-Acts 15:23-29 (NKJV), emphasis added
In short, the answer to why we Christians “pick and choose” the laws we follow is out of obedience to the Apostles themselves, not personal choice. The other laws of the Torah are not required for converts to Christianity. We are to simply avoid partaking of those things offered to idols, from consuming blood or things strangled, and from sexual immorality.
In order to define these things, we must examine what an early Gentile convert would have been exposed to, namely, their definitions within the Torah. Thus, all the prohibitions against sexual immorality, including Leviticus 18, are indeed still binding on Christian converts today.
Ultimately, the Apostles in their wisdom placed no greater burden from the law upon converts than those few commands. We need not maintain full obedience to the Torah, we need not be circumcised, we need not follow any dietaries laws except those stated. This fits perfectly with what else we see in the Early Church, and how they lived.
Even St. Peter, a Jew, is given permission to eat meat previously forbidden (Acts 10:15). Christ Himself tells those who would follow him that the burden of believers is light (Matthew 11:28-30). St. John says of Christ’s commandments that they are not burdensome (1 John 5:2-3).
While there are many additional expectations of Christian behavior, the Apostles deemed it necessary to comment specifically on how the Torah is to be obeyed among converts.
Also, stop eating blood sausage.