Athanasius’s account of the Incarnation is one of those ideas so logical and simple that, once you get it, you always feel like explaining it takes ten times more words than necessary.
1.) Man, created from nothing, is an animal who was given the likeness to the Logos.
2.) Man lost his likeness to the Logos, and so necessarily fell back to nothing – to corruption and death.
3.) Death therefore became necessary, but the Logos could not stand to lose those who were in his likeness.
4.) Death therefore had to somehow re-establish likeness to the Logos: but the only way death could re-establish likeness to the Logos is if the Logos himself died.
5.) The Logos could not die if he did not have a body.
6.) The Logos therefore unified a body to his person, such that whatever happened to the body could be said to be done to the person.