Jesus is the only one who has demonstrated the ability and the authority to fulfill all three of these offices in combination in one person.
The first observation that I need to make is that there is mystery here. We must acknowledge that complete understanding of this is beyond our reach as humans.
In the last few months, I have been reading about the first Ecumenical Councils of the church in the 4th and 5th Centuries. It was at these councils that the nature of Jesus was clearly defined for all of Christendom. Many of the misunderstandings about Jesus that survive today were addressed by these councils.
We like to think of ourselves as free moral agents with the ability to control our own destinies. We don’t want to have anyone tell us what we can or can’t do. We are taught that such freedom is our birthright and no-one should be able to take this away from us.