nature" of a thing we mean the combination of all the
qualities that make the thing what it is. By the "substance" of a thing
we mean the part that never changes, and which cannot be changed without
destroying the nature of the thing.

Q. 196. {30} Can we fully understand how the three Divine Persons are
one and the same God?
A. We cannot fully understand how the three Divine Persons are one and
the same God, because this is a mystery.

Q. 197. {31} What is a mystery?
A. A mystery is a truth which we cannot fully understand.

Q. 198. Is every truth which we cannot understand a mystery?
A. Every truth which we cannot understand is not a mystery; but every
revealed truth which no one can understand is a mystery.

Q. 199. Should we believe truths which we cannot understand?
A. We should and often do believe truths which we cannot understand when
we have proof of their existence.

Q. 200. Give an example of truths which all believe, though many do not
understand them.
A. All believe that the earth is round and moving, though many do not
understand it. All believe that a seed planted in the ground will
produce a flower or tree often with more than a thousand other seeds
equal to itself, though many cannot understand how this is done.

Q. 201. Why must a divine religion have mysteries?
A. A divine religion must have mysteries because it must have
supernatural truths and God Himself must teach them. A religion that has
only natural truths, such as man can know by reason alone, fully
understand and teach, is only a human religion.

Q. 202. Why does God require us to believe mysteries?
A. God requires us to believe mysteries that we may submit our
understanding to Him.

Q. 203. By what form of prayer do we praise the Holy Trinity?
A. We praise the Holy Trinity by a form of prayer called the Doxology,
which has come down to us almost from the time of the Apostles.

Q. 204. Say the Doxology.
A. The Doxology is: "Glory be to the Father, and to the Son, and to the
Holy Ghost. As it was in the beginning, is now, and ever shall be, world
without end. Amen."

Q. 205. Is there any other form of the Doxology?
A. There is another form of the Doxology, which is said in the
celebration of the Mass. It is called the "Gloria in excelsis" or "Glory
be to God on high," &c., the words sung by the Angels at the birth of
Our Lord.

LESSON FOURTH.
ON CREATION.

Q. 206. What is the difference between making and creating?
A.