The kind of spirit to which Peter referred in 1 Peter 1:11 is like the Holy Spirit referred to in other scriptures. This kind of spirit can manifest itself. In the case of the Spirit of Christ, one manifestation was the manifestation of becoming flesh. Previous manifestations had been by exerting influence in ancient times over prophets to lead them towards truth regarding this Christ. Also visions (example Isaiah 6) and other manifestations which were akin to something even more physical in the here and now (examples Daniel and Enoch).
