Jesus’ witnesses against unbelief: Jesus’ works provide testimony greater than John the Baptist’s. The gospels constantly speak of the amazement of the crowds. The people’s testimony that he has done all things well alludes—probably unconsciously—to God when he looked at all his creation and called it good (Gn 1:31).
To take only one example, Peter has witnessed many miracles of Jesus. He has seen healings, including the cure of his mother-in-law and the changing of water into wine. But these miracles do not touch him as much as the miraculous number of fish caught at Jesus’ bidding does. He does know fishing, and he can testify that what he has just experienced is extremely unusual, to say the least.
These kinds of works show Jesus to be God. But to recognize a miracle—or a person—one must have an eye that really sees.