When one steals knowledge (Gneivas Daas) and gets caught by witnesses, how does he pay back double?
PS. Why is there no Gzeilas Daas?
By the very act of the theft he's already paid it back double.
How so? דעת equals 474, so a double payment for that would be 948. This is the gematria of the verse (Ps. 116:11):
אני אמרתי בחפזי כל האדם כזב
"I said in my haste, 'All people are deceitful.'"
- which is what the victim now knows to be true in one more case than he did before.
As for why there is no 'Gzeilas Daas' the answer is simple! Someone stole and destroyed the concept from Jewish Law and Thought. There was a Gneivas Daas of Gzeilas Daas!!