30. Angels and spirits are human beings, as is evident from their being seen by Abraham, Gideon, Daniel and the Prophets, and especially by John when he wrote the Book of Revelation, as well as by the women in the Lord's tomb. Indeed the Lord Himself was seen by the disciples after the resurrection. The reason why they could see them is that the eyes of their spirits were then opened; and when this happens angels are to be seen in their own form, which is the human one. But they are invisible when those eyes are shut, that is, obscured by the sight of eyes which draw all their impressions from the material world.