That' refers to the whole concept of salvation. It is a great error to teach that God gives us faith. The Scriptures are plain. Faith is our responsibility before God. Faith comes by hearing the Word of God.
Common sense shows that faith is our responsibility.
The doctrine of Calvinism, that God gives faith to some and not to others, is a damnable heresy. Jesus said that if Sodom and Gomorrah had had the advantages of the Jews, they would have repented. He upbraided the cities which saw His power, but would not repent. Calvinism makes God a tyrannical parent who demands from his child that which the child cannot possibly do. This is blasphemy.