form... with substance

"Hold fast the form  of sound words which you have heard among many witnesses,"  was the admonition St. Paul  gave to his son in the faith Timothy.  True  religion has a form and content.  People ask,"why do we worship this way?"  well, the essential structure was given to us, and the basic  elements of our Faith, which the Church elaborated upon as She matured in grace and truth. This explains why  we have an apostles creed that predates the Nicene of 325.  It does not contradict, but we accept the growth in understanding (NB  not  growth in doctrine).  The Church's self reflection and understanding of  the Sacred Deposit  matures.  The structure- the form  of that Truth  doesn't change, while the particular details might.  Take for instance the structure of the Liturgy. The Church  has always had the basic structure we have, and been consensus it elaborated on it's expression of it. Therefore in the 500s the chanting of the Creed  was added to the liturgy. And we could go an  near infinitum.