The setting for today's passage is once again the Temple and its immediate vicinity. That the glory of God would return to the Temple after departing (per Ezekiel's prophecy) is something St. John continually draws out in his Gospel account. Jesus' walking and teaching in the temple is an important instance of fulfilled prophecy. The Jews pick up stones to stone Jesus right after He says "I and the Father are one." They realize what He says makes Himself equal with God. Their assessment was correct, but what went wrong?
As mentioned in previous posts, there was a narrow and confined human expectation of God's salvation and self-revelation brought about by a habitual inward turning. "God could not possibly do this, therefore it goes against the TaNaKh [law, prophets, and writings], must have been the thought. Jesus then challenges them from their very own scriptures, as we read in one of the more challenging texts in the New Testament. "Is it not written in your Law 'I said, you are gods'?" This quote from Jesus references Psalm 82:6, which says "I said, 'You are gods, sons of the Most High, all of you."
Much has been written on Psalm which would take us far afield. It is a beautiful and interesting Psalm! The point I think Jesus is making in this context, though, is that those to whom the law was given have authority (along with responsibility). They were given divine authority to govern and rule in accord with the revelation God had provided, which was in certain sense a reflection of Himself. In Psalm 82, the judges failed in their objective just like many of the Jewish leaders had failed in Jesus' time. Specifically, they were failing to recognize that Jesus was not blaspheming by claiming to be the Son of God, nor was He committing blasphemy by implying this meant equality with God.
Jesus is saying that God did something in the past as He is doing now. The hearers who truly knew their Scriptures - that the Scripture cannot be broken - should have been able to understand. Only, what was occurring now is much more profound than anything in the past. The profundity is evident in the signs Jesus does, to which He directs the audience (John 10:37-38).