Themes from Acts : Number 1. Acts of the Apostles as a Treatise.

Act 1:1  The former treatise I made, O Theophilus, concerning all that Jesus began both to do and to teach,

The former treatise I made,
A TRE'ATISE, n. [L. tractatus.] A tract; a written composition on a particular subject, in which the principles of it are discussed or explained. A treatise is of an indefinite length; but it implies more form and method than an essay, and less fullness or copiousness than a system. Webster’s 1828 Dictionary.
Treatise Greek (Logos)Thayer :1e) anything reported in speech; a narration, narrative 1f) matter under discussion, thing spoken of, affair, a matter in dispute, case, suit at law 1g) the thing spoken of or talked about; event, deed

The former treatise refers to the Gospel of Luke.Meaning the Gospel written by him the Evangelist Luke, for from that he makes a transition to this, beginning here where he there left off; namely, at the ascension of Christ; see Luk_24:51.
Luk 1:1  Since many have been disposed to write narratives of those events, of which we have full assurance,
Luk 1:2  as they delivered them to us, who from the first were eye-witnesses and ministers of the word;
and it seemed proper for me also, as I had examined them all accurately, to write out the whole, methodically, for thee, excellent Theophilus:
Luk 1:4  that thou mayest know the truth of the statements, which thou hast been taught.

Both the Gospel and the Acts  of the Apostles were written to Theophilus.#

The word Theophilus (Theophilos) means “a friend of God,” or a pious man; and it has been supposed by some that Luke did not refer to any particular “individual,” but to any man that loved God; but there is no reason for this opinion. Significant names were very common, and there is no good reason to doubt that this was some individual known to Luke.

concerning all that Jesus began both to do and to teach,
To do and teach - These two words comprise his miracles and sermons. This introduction seems to intimate that, as he had already in his Gospel given an account of the life and actions of our Lord, so in this second treatise he was about to give an account of the lives and acts of some of the chief apostles, such as Peter and Paul. A.C
Luke’s gospel describes what Jesus began to do and to teach. It suggests that he now continued His actions and his teaching through his chosen ministers. The Lord always combines actions - expressions of His Love and Grace through miraculous signs and wonders even today.

Applications.
1.  Luke researched the truth of what Jesus did and taught. So should we. Are you a scholar of the Works and words of Jesus. You should be and you should write down what you have found out.
2. Is you Christianity just cerebral. May it be firstly practical and then didactic.