Not to advance is to go back.

"Is" in that fragmented sentence is saying that "is to go back" is another possible way of saying "not to advance."

Hi,Thanks a lot Key1.As your teaching, could I have it rephrased: To say not to advance is to say to go back. So, the [is] shows [to go back] is the same as [not to advance].The [is] should be considered as being causative verb.

Hello Key1,Would you be kind to let me ask the futher question? And could you tell me the understanding correct or not?In [The book is to be read by every student.], the [is] used to the speaker to show [the book] like the property of [the book to be read by every student]. Because the speaker not makes [the book] typically have the quality to be read by every student. And just assign [the book]

The book is the subject in the sentence and the predicate is "is read." Student is the object of the verb. In other words "is" belongs to the book.

Yes, it can be rephrased like that.

Hi, It is very kind of you to teach me so lot.If you like do, I have a need for your help. 1. The [is] in the following sentence is the same?{The way to be safe is never to feel secure.}2. The [is] in the following sentences are different from each other. {What is in the mind.} ------the [is] = belongs to ; because [what] is cantained or surrounded by the mind.{What is on the mind.}------the [is]