site:www.newadvent.org/fathers/ Peter keysSubstitute for the bold words "Peter keys" with whatever keywords you want. Then paste the whole line into Google's search field, and that's it!
The search will turn up pages at New Advent of Church Fathers and councils containing those keywords. Click here to see what the search results for the above looks like. Try your own keywords on various topics or even include a Church Father's name, such as "Chrysostom priest" to see texts of St. John Chrysostom containing the word "priest." The sky's the limit––baptism, Liturgy, purgatory, sacrifice, whatever you wish! This is not an exhaustive search, of course, as New Advent does not contain every single text from ECFs, but it is very useful all the same.