If someone found an object before the owner gave up hope.
תא שמע...וכדרבי יצחק
Lines  15-29Gemara
The Gemara brings four proofs that the halacha follows Rava - that yiush without knowledge is considered yiush.
ת"ש המוצא...מלקטי ליה
Lines  29-41Gemara
The gemara brings two proofs like Rava - that yiush without knowledge is considered yiush. The gemara knocks off both of those proofs.
ת"ש קציעות...נפילתה נמאסת
Lines  41-53Gemara
The Gemara tries to bring proof like Abaye since it says you can’t keep olives that blow off the tree. The Gemara answers that since you can tell the olives are from the tree the owner won’t give up hope.
תא שמע הגנב...תרי גווני גזלן
Lines  53-5Gemara
The Gemara brings the 8th Ta Shema which is a proof like Rava once again. The Gemara answers that it’s not a good proof