In Mark Schuler textbook (pp.214-215), who was the original addressee of Luke (and Acts)?

I have no information about this Mark Schuler and his textbook.

Luke 1 King James Version (KJV)
1 Forasmuch as many have taken in hand to set forth in order a declaration of those things which are most surely believed among us,
2 Even as they delivered them unto us, which from the beginning were eyewitnesses, and ministers of the word;
3 It seemed good to me also, having had perfect understanding of all things from the very first, to write unto thee in order, most excellent Theophilus,
4 That thou mightest know the certainty of those things, wherein thou hast been instructed.

"Theophilus" means "Beloved of God", and verse 4 explains that the book is addressed to members of the church who have been instructed.