To preserve an unbroken domesticity was essential to his peace of mind; he would not have known where his hair-brushes were, or how to provide stamps for his letters, if Mrs. Welland had not been there to tell him.
There are no more uses of "essential" in the book.
Show samples from other sources
The essential feature of the pen is that it writes so consistently.
I carry all the essential tools and materials I need in this toolbox.