If it were certain that the only way to provide a comfortable existence to future generations involved substantial cutbacks toward a lifestyle having far fewer energy and material comforts today, do you think humanity would voluntarily do so? Can we leave treats on the shelf, within easy reach? If so, is it only uncertainty that prevents us? If not, what do you see as the barriers?

The exercise asks whether people would voluntarily choose to live with less energy and material comforts today in order to secure a comfortable existence for future generations. The student should also consider if only uncertainty prevents us from making these changes and identify the barriers that hinder making sacrifices.

In order to give a comprehensive answer to this question, let's identify some possible barriers that could prevent people from making voluntary sacrifices for a more sustainable future. Some possible barriers could be: 1. Selfishness and comfort: People might not be willing to give up their current lifestyle and conveniences. 2. Short-term thinking: It's human nature to prioritize short-term goals over long-term consequences. 3. Economic interests: The economy might prioritize growth over sustainable living. 4. Lack of education and awareness: Many people don't have a strong understanding of sustainability or why it's essential for the future.

Another part of this exercise is to analyze the effect of uncertainty on making voluntary changes for future generations. It is possible that due to uncertain outcomes, people might be less likely to make sacrifices. The lack of clarity regarding the effectiveness of individual actions on the larger scale could be a major factor in preventing people from making these changes.

To foster critical thinking and a more in-depth understanding of the issue, the student can consider the following points for discussion: 1. Are there examples of societies or communities that have made similar sacrifices in the past? 2. What measures could governments or institutions take to encourage individuals to make these sacrifices? 3. Is sustainable living and maintaining material comforts mutually exclusive? Can there be a balance? 4. How can education and awareness campaigns be more effective in promoting sustainable living? By considering these points and analyzing the barriers, the student can come up with a well-thought-out response to the exercise on whether humanity would voluntarily make sacrifices for future generations' comfortable existence.