What is the theme of Part 1 of Fifth Business?
It may be a mistake to try to ascribe themes to parts of books since authors generally work from one overarching theme. Yet, if ia trend can be seen in particular sections, the term "theme" may be broadly applied if the result does not undermine the author's overall objective, and this assumes that author's do have intention and objectives that are communicated through their texts.
With this said, one trend that presents itself in Part I is what might be stated as: Small individual acts have the potential for devastating effects. This reflects the injury to Mrs. Dempster, her unfortunate incident with the tramp, Willie's death and other events in Part I.