When Hooper visits Brody's home, he brings two bottles of wine. Brody pours himself a large measure, and then gives his wife and Hooper some. If you look at the bottle, firstly it seems rather full for the amount he's just poured, and secondly the level changes from shot to shot. Sometimes it's above the label, sometimes below.
The purpose of an Essay Introduction is to introduce the reader to the subject matter you are writing about and to state the intent of the paper.
This paper examines . . ., The aim of this paper is to . . ., and The purpose of this essay is to . . . A purpose statement makes a promise to the reader about the development of the argument but does not preview the particular conclusions that the writer has drawn. A purpose statement usually appears toward the end of the introduction.