In 1 Corinthians 8:1, what does Paul say 'puffs up,' while love builds up?

Answer: Knowledge

On food sacrificed to idols, Paul writes, "Knowledge puffs up, but love builds up" (KJV: "charity edifieth").

“Now about food sacrificed to idols: We know that we all have knowledge. Knowledge puffs up, but love builds up.”— 1 Corinthians 8:1 (BSB)