The phrase "knows no alternative" suggests that there is no other choice or option available. Some synonyms for this phrase include "has no substitute," "cannot be replaced," and "has no equal." These expressions indicate that something is unique or necessary and cannot be replaced or substituted by anything else. Other synonyms for "knows no alternative" include "cannot be avoided," "inevitable," and "unavoidable." These words imply that something is bound to happen or exist, and there is no way around it. Therefore, when using synonyms for "knows no alternative," it is essential to choose the right words that convey the intended meaning and context effectively.