The project rationale is perhaps the most important element of a project proposal. While other parts of a proposal concern themselves with details on how a project would be carried out, the rationale explains why the project is worth doing in the first place. Whether you're pitching a project or having one pitched to you, the pitch must provide a compelling reason for committing resources to this project rather than something else.
Justifying the Project
Within a proposal, the rationale may be referred to as the "needs assessment" or the "problem statement." Whatever it's called, it must provide clear evidence of why this project is necessary. It's easy to fall into the trap of circular reasoning here, so be cautious. For example, say the proposal is for a new parking garage where there is currently only a parking lot. The simple lack of an existing garage is not a sufficient rationale for building one. Nor does the fact that it's possible to build the garage provide an acceptable argument that it must be built. The rationale should explain why the current parking situation is insufficient, how the garage would remedy that insufficiency, and why the garage plan would be a wise use of this particular space.