Albert Barnes on John 18:20

Openly to the world. If his doctrine had tended to excite sedition and tumult, if he had aimed to overthrow the government, he would have trained his friends in secret; he would have retired from public view, and would have laid his plans in private. This is the case with all who attempt to subvert existing establishments. Instead of that, he had proclaimed his views to all. He had done it in every place of public concourse--in the synagogue and in the temple. He here speaks the language of one conscious of innocence and determined to insist on his rights.

Always resort. Constantly assemble. They were required to assemble there three times in a year, and great multitudes were there constantly.

In secret, &c. He had taught no private or concealed doctrine. He had taught nothing to his disciples which he had not himself taught in public and commanded them to do, Mt 10:27, Lk 12:3.

(n) "I spoke openly to the world" Lk 4:15, Jn 7:14,26,28, 8:2 (o) "in secret have I said nothing" Acts 26:26