In the Session 12 of A Study of Philippians on Philippians 4:14–23, students consider the question, Can I really afford to give generously?
To get them thinking about generosity, ask if they know what a zero-sum game or relationship is and some examples. Zero sum refers to “a situation [as a game or relationship] in which a gain for one side entails a corresponding loss for the other side, e.g., dividing up the budget is a zero–sum game” Merriam-Webster Dictionary.
The most famous example of a zero-sum game is called the prisoner’s dilemma. This video explains it. 
In modern terms, the question is whether we face zero-sum situations where if I give, I lose. The thinking can go, there’s only so much resource available, so if I give some of mine away, there’s less for me.
Some examples include: If I help my sports teammates score, I won’t score as many points myself in a game. Letting a classmate ask a question first in class may mean that I won’t get a chance to pose my question. If I tithe on the earnings from my part-time job, I might not have date money for Friday night. Time talking with a church visitor could keep me from chatting with my friends. Time helping a classmate with a tough subject might keep me from my own studies.
How does God want us to consider acts of generosity? As zero-sum situations or something else? Is it possible that we evaluate losses and gains in ways that aren’t biblical? Help your students evaluate that in this session.
As with any video, watch the whole thing yourself ahead of time to be sure it’s appropriate for your group.
What were your students’ reactions?