The phrase "the whole idea" can be used to describe a concept or notion. However, there are several synonyms that can be used in place of this phrase to add variety to your writing. For example, you could use the term "the overarching concept" to suggest a comprehensive idea or theme. Alternatively, you could use terms such as "the basic premise," "the underlying notion," or "the fundamental idea" to convey the foundational concept in your writing. Other possible synonyms for "the whole idea" include "the central theme," "the primary principle," or "the core concept." Whatever word or phrase you choose, selecting an appropriate synonym can help enhance the meaning and impact of your writing.