A proposal is exactly what it sounds like: it proposes an idea, a statement of purpose, and provides evidence intended to convince the reader why that idea is a good or bad one.
This section should be brief and only discuss what your actual proposition is. Do not include details about how you will carry out the proposal in this section.
The word cap is very important because it allows you to be very specific about your argument/topic and also allows conveners to judge quickly whether or not your proposal is in line with the overall general topic of the conference.
