"Ye have heard how I said unto you, I go away, and come again unto you. If ye loved me, ye would rejoice, because I said, I go unto the Father: for my Father is greater than I." John 14:28
John 14:28 if frequently applied to in order to argue against the Trinity teaching that Jesus and the Father are equal.
Response:
The term "greater" is applied to one who is served by others: servants serve one that is "greater" than themselves.
Luke 22
26: But ye shall not be so: but he that is greatest among you, let him be as the younger; and he that is chief, as he that doth serve.
27: For whether is greater, he that sitteth at meat, or he that serveth? is not he that sitteth at meat? but I am among you as he that serveth.
In Luke 22:27 the one who is served is said to be "greater" than the one who serves: "For whether is greater, he that sitteth at meat, or he that serveth? is not he that sitteth at meat?. . . "
The one who is served is "greater" by position than the one who serves. Even though the one who is served is greater by position than the one who is served they are both equal in terms of nature (ie. they are both equal in terms of their humanity).
In the same way Jesus when He became a man took upon himself "the form of a servant" (Phillippians 2:7) Jesus as a servant was positionally lower then the Father. As a servant Jesus could say that the Father was "greater than" he, just as the one who is served is said to be "greater" than the one who serves (Luke 22:27).
However, just as an earthly servant is equal by nature to his master, so Jesus by nature is equal to his Father. The Trinity teaches that Jesus and the Father are equal in terms of nature, but allows that the Father was greater by postion when Jesus became a servant.
Interestingly the Bible says that Jesus "took upon him the form of a servant":
"But made himself of no reputation, and took upon him the form of a servant, and was made in the likeness of men:" Phillippians 2:7
The phrase "took upon him the form of servant" would seem to indicte that prior to the time of talking on thre form of a servant that Jesus was not then in the form of a servant. This is a poweful argument that Jesus and the Father were positionally equal prior to the incarnation. This would also seem to contradict the Watchtower premise that Jesus existed as "a servant" for millions of years prior to the incarnation.