I Thess 4: Four Unities
13, But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope.
14, For if we believe that Jesus died and rose again, even so them also which sleep in Jesus will God bring with him.
15, For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent them which are asleep.
16, For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first:
17, Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord.
18, Wherefore comfort one another with these words.
I think Aristotle wrote also about unities in his Poetics, but I am referring to four different unities altogether, much more important, having to do with the Rapture and the union of living believers with those who had died in Christ. Studying this as we see it in Thessalonians is very important because it shows clearly the nature of the Rapture.
It also shows why both the modern futurist view of the rapture and the Max King variant of Preterism overlook (and I am being kind) key points of doctrine found in this chapter.
The four unities are unity of time, action, essence, and place.