OUTLINE:

“in vain”
To Paul, Christ’s resurrection was fundamental to the faith; he was saying that if Christ wasn’t resurrected, then our faith is worthless

Jn 8:56
“Your father Abraham rejoiced to see My day, and he saw it and was glad.”

Ac 9:4-5
and he fell to the ground and heard a voice saying to him, “Saul, Saul, why are you persecuting Me?” And he said, “Who are You, Lord?” And He said, “I am Jesus whom you are persecuting,

Ro 4:25
He who was delivered over because of our transgressions, and was raised because of our justification. [the resurrection of Jesus Christ was proof that God had accepted His sacrifice, that God would be just in justifying the ungodly]

Jn 8:24
“Therefore I said to you that you will die in your sins; for unless you believe that I am He, you will die in your sins.”

1Co 15:17
If this (errant) logic were true, we’re in no better condition, positionally than the unbelieving Jews that crucified Jesus!!!

“in this life only”
Assuming there is no resurrection, we’d have nothing to look forward to (even Jesus would still be in the grave, not seated at the right hand of the Father in Heaven)

1Th 4:16
For the Lord Himself will descend from heaven with a shout, with the voice of the archangel and with the trumpet of God, and the dead in Christ will rise first.

1Th 4:17
Then we who are alive and remain will be caught up together with them in the clouds to meet the Lord in the air, and so we shall always be with the Lord.