The Catholic Church did not invent the idea that the Holy Spirit proceeds from the Father and the Son. The teaching is not only implied by Scripture but it was explicitly taught by the Early Fathers as well. This article may help others understand the Catholic position:
Straight Answers, The Wording Of The Nicene Creed, by Fr. William Saunders
The Church's Scriptures on the Filioque Clause:
The Holy Spirit will be sent from Jesus and His Father.
26 But when the Counselor comes, whom I shall send to you from the Father, even the Spirit of truth, who proceeds from the Father, he will bear witness to me; 27 and you also are witnesses, because you have been with me from the beginning.
John 15:26-27
