Sentence:  The ninth century was in its artistic work `` the spiritually freest and most self-sufficient between past and future '' , and the loving skill spent by its artists upon their products is a testimonial to their sense that what they were doing <WSD>was</WSD> important and was appreciated . 
Meaning of the word marked with <WSD> tags:  have the quality of being; (copula, used with an adjective or a predicate noun)