I recently read an article in which the writer stated that he did not believe in a triune God. This concept, which is professed by Christians, says that God is of one essence, but consists of three persons that are equal in nature. These three are God, the father; Jesus, the son; and the Holy Spirit. The writer goes on to say that the Trinity is not possible because there is only one mention of the Holy Spirit in the Book of Revelation. Clearly, this writer has ignored the remaining books and does not give credibility to the words of Jesus concerning the Holy Spirit.
In Mathew 28:18-19 Jesus said, "All authority in heaven and on earth has been given to me. Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit."
At the time of His ascension Jesus said to His disciples, "But you will receive power when the Holy Spirit comes to you," Acts 1:8.
John 16:5-16 makes it clear that the Holy Spirit is not to be found in Heaven, but with us and in us. In John 16:7 Jesus makes this very clear when He says, "It is for your good that I am going away. Unless I go away, the Counselor will not come to you; but if I go, I will send him to you."
John 14:15-31 is also very clear about the existence of the Holy Spirit; specifically John 14:16 where Jesus says, "And I will ask the Father, and he will give you another Counselor to be with you forever." Also, John 14:26 where Jesus says, "But the Counselor, the Holy Spirit whom the Father will send in my name, will teach you all things and will remind you of everything I have said to you."
Jesus' words are enough to convince me that the Holy Spirit does, in fact, exist and is a vital part of the Trinity. He does not exist in heaven; but right here with you and me guiding everyone who truly loves Jesus and believes that He is their Savior.
I would also like to offer an example that might help make the concept of the Trinity a little more understandable. If you hold an apple in your hand, you are holding one apple which consists of three parts: pulp, seeds, and peel; ie: 3 in 1. Without the seeds the pulp and peel are nothing. Without the peel the pulp and seeds are nothing. Without the pulp the seeds and peel are nothing. You must have all three to make one apple. They are three separate and distinct parts, but all are necessary to make one apple.
If an apple can be 3 in 1, is it so difficult to imagine that God, with whom all things are possible, could also be 3 in 1. Yes, the Trinity does exist and Christians worship one God consisting of three inseparable persons.