Sentence:  In contrast to this Stoic patristic view , Utopia implies that the nature of man <WSD>is</WSD> such that to rely on individual conscience to supply the deficiencies of municipal law is to embark on the bottomless sea of human sinfulness in a sieve . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)