1 Corinthians 8:7 (ESV)

7 However, not all possess this knowledge. But some, through former association with idols, eat food as really offered to an idol, and their conscience, being weak, is defiled.

Only now does Paul really begin to address the Corinthians’ questions. He begins with a startling statement, that not all (meaning, not all the members of the church) possess this knowledge, the knowledge that there is only one God, and that idols have no existence.

Paul’s meaning becomes clearer in 1 Corinthians 8:9. It is not that some church members have not been taught this fundamental truth, or that they do not confess it. It is rather that some are weak and may easily stumble. Having come from a life of idolatry, these church members are not yet firm in their faith in the one true God. They can easily be tempted to fall back into idolatry.

The following part of the verse is not so easy to translate or interpret. According to one popular interpretation, Paul’s meaning is that some believers will imagine that they are sinning when they eat food that was offered to idols. Because these believers are weak in the faith, their conscience will be unnecessarily burdened by sacrificial food.

But the above-mentioned interpretation does not take into account Paul’s warnings in 1 Corinthians 10:1–33, whereby he strongly reiterates the apostolic command to abstain from food that was offered to idols. Also, this interpretation fails to take seriously Paul’s statement that the eating of sacrificial food leads to a believer’s conscience being defiled (not simply burdened). 

A literal translation would read, But some, after the habit, until now, of the idol, eat [the food] as food that was offered to idols... Paul then seems to be referring to an idolatrous habit that accompanied the eating of sacrificial food, a habit that a weak believer would not be able to resist.

It is very possible that Paul has in mind the drink offering, which was customarily drunk before, during, or after the meal. The drink offering was accompanied by a prayer in which the idol was thanked for the meal. This idolatrous practice also existed among the apostate Israelites in the time of the prophets (Isaiah 65:11).

A person’s conscience can be described as weak when it does not succeed in leading him to do what is right. When a believer, because of the weakness of his conscience, partakes in idolatry, his conscience is defiled (in other words, stained or polluted). Practically, this might mean that such a person becomes more and more hardened in his sin.