On what basis does Thomas Aquinas say that the Church existed since the time of Abel? In Aquinas' Expositio in Symbolum Apostolorum (Explanation of the Apostles' Creed), his explanation in Article 9 of the Church being &quot;catholic&quot; includes this statement:

Nam aliqui dixerunt, quod Ecclesia debet durare usque ad certum tempus. Sed hoc est falsum: quia haec Ecclesia incepit a tempore Abel, et durabit usque ad finem saeculi…
Some have said that the Church will exist only up to a certain time. But this is false, for the Church began to exist in the time of Abel and will endure up to the end of the world…

I presume that the Abel he is referring to is the one of Cain and Abel in Genesis. Unfortunately, Aquinas doesn't explain in this text his reasoning for why the Church began to exist at this time, as opposed to with Adam and Eve, with any of the Jewish heroes of faith, or with Jesus.
On what basis does Thomas Aquinas say that the Church existed since the time of Abel?
Abel was the first to offer sacrifice pleasing to God.
cf. You Shall Worship One God: The Mystery of Loving Sacrifice in Salvation History by Fr. Philippe, O.P., ch. 1, §&quot;Sacrifice Before the Law&quot;
Adam did offer sacrifice (to offer sacrifice as part of our nature), but it seems it was not pleasing to God on account of his Original Sin. According to St. Thomas Aquinas (Summa Theologica II-II q. 85 a. 1 ad 2),

Perhaps the reason why we read of no sacrifice being offered by Adam may be that, as the origin of sin is ascribed to him, the origin of sanctification ought not to be represented as typified in him.

Also, &quot;the time of Abel&quot; (&quot;tempore Abel&quot;) needn't exclude Adam.
One can only offer pleasing sacrifice to God in His Church.
St. Thomas quotes 1 Cor. 10:20 in Expositio in Symbolum Apostolorum article 1, when discussing four different motives that lead man to worship false gods:

the things which the heathens [gentes, έθνη] sacrifice, they sacrifice to devils, and not to God.

St. Paul distinguishes heathens/gentiles (gentes, Έλλησιν) and Jews from members of the Church of God (&quot;ecclesiae Dei&quot;, εκκλησία του θεού) in v. 32.
Thus, the Church could be defined as that group of people which offers pleasing sacrifice to God.